I'm getting tired of people leaving comments about other people's pets under the guise of being 'concerned' for them and trying to 'educate' the owner, but in reality, they have absolutely no idea what they're talking about.

You see it a lot here: people judging someone's entire pet keeping system on ONE photo or ONE statement.
I'd say, rather than accusing people of things, ASK them about the issues.

Rather than saying 'your rats are going to die if you keep them on pine bedding!' and making an assumption that what you're seeing is pine, ASK 'what kind of bedding is that?'
If the answer is pine, THEN you can give out the info. But don't just assume.

Before accusing someone of having an obese animal, ask if the animal is overweight in reality or if its just the angle of the pic/seasonal coat of the animal.

Before assuming someone keeps their rat in an unsuitable cage, ASK first if that is the animal's permanent cage, or whether it is just in that cage for the photo/transport to the vets/as a hospital cage.

Before assuming someone is an irresponsible owner because their dog is not neutered, ask WHY is isn't, many people don't believe in neutering their pets as it can affect their health and they're not necessarily just 'irresponsible' owners.

Before assuming a doberman 'isn't a pure bred dobe' because it has a full tail and ears, EDUCATE yourself on the breed and realise that in many countries, removal of the ears and tail is illegal and a cropped and docked dobe would look weird to US! (getting a dobe pup soon, with full tail, ears and dew-claws. Im looking forward to the comments from USA folk who ask me what breed it is because it doesn't look like the majority of their dobes!)

Before assuming a rat lives alone because there is only one rat in the photo, ASK if the rat has a companion; it may very well just be a photo shoot for that one individual, and he has a bunch of friends 'off scene'.

I could go on, but you get the idea.
We cannot tell much about an animal's life, its situation and its health from one single pic. If we are concerned by the presence, or absence, of something in the pic, ASK before outright accusing.

Also......PLEASE know your shit before you try and educate other people. There is nothing more pathetic than seeing someone leave a comment on someone else's animal trying to 'educate' them, when they are completely clueless themselves and are doing more damage by spreading false information!

For example, a friend recently had a comment aimed at her that 'lone rats will die of depression' and 'once a rat has a respiratory infection, its impossible to cure'.
Both bullshit.
Lone rats are bored, under-stimulated, unhappy and potentially suffer more health and behavioural problems, as well as an estimated shorter life. BUT......I've never known one to die from not having company.
I get loads of lone rats come into my rescue, rats that have been alone their entire lives, AND rats that have once known companionship and have lost their cage mate. They've all been very alive, and none have ever 'died of loneliness' before I could get to them!

Respiratory infections? The key word there is 'infection'. Infections are not permanent, nor incurable. Everyone reading this will have had an infection of some kind in their life, and we're cured now, aren't we?
There is something called 'antibiotics' which are very effective at treating most infections!

Now, I get what the person was trying to say 'lone rats are a bad idea, and respiratory infections are best avoided', but the way they went about saying it just made them look ignorant due to the addition of misinformation.

I've seen it a lot in rat communities: people give 'advice' when they have no business giving advice. Sure, they're trying to help, but you do more harm than good when you give out false information.
If someone asks me a question about rats that is outside of my knowledge, I will say so, I don't just guess the answer and pretend I know what I'm talking about.
Its dangerous.

I remember once seeing someone asking for nutrition advice for their ailing rat, and wanting ideas on what foods would be good to build him up. Someone suggested scrambled egg and fish, both very nutritious foods for rats which do them a lot of good, and are not bad ideas when trying to help a sick rat recover.
Someone then came along and left a statement akin to 'vegan foods are far better for rats, I'd go for nutritious non-animal products if I were you' or words to that effect. Because this particular person was a vegan themselves and had 'vegan' rats (in inverted commas since I believe veganism is a lifestyle and mindset based on one's personal morals and beliefs, and a rat cannot make a choice like that, ergo, they cannot be 'truly' vegan to me as it is forced on them, not chosen by them, and, to me, veganism is a very personal choice).

This was potentially dangerous.
The owner asking the advice was a novice owner, and likely to believe anything an older more experienced rat owner told them. And omitting animal products from a rats diet at the BEST of times takes very careful planning, if it ever can be said to work at all. Owning vegan rats is not something one should leap into on a whim or on one piece of advice.
But this owner was ready to drop the eggs and fish and lean chicken on this one comment. And seriously? If you're trying to bulk up a rat, particularly a young rat, these foods are without a doubt, the BEST foods to use.
So by following this advice, she was potentially putting back her rat's recovery and causing him more damage.

This is the problem with the internet: anyone can give anyone else advice, when they have no experience or information under their belt that qualifies them to do so. And people will often believe things others tell them without checking it out first, particularly if that person is a 'known' figure in the rat community and has had rats a long time.

I wouldn't dream of commenting on a picture of, say, a horse and spurting out advice on horse care. Because I know little about horses. Oh, my mum used to own one, I spent a lot of my childhood at the stables, playing in the hay bales (and waiting to catch a glimpse of wild rats), but that doesn't mean I know enough about horses to be giving out advice to anyone, about any horse issue, just because I grew up with one.

Unfortunately, people are ready to open their mouths and act as teacher when they really don't have the experience and knowledge to do so.
Or at the very least, if you're going to advise someone on something you're not an expert at yourself, word yourself to make them aware that you're not an expert yourself. The addition of terms like 'I have heard' or 'Im not sure on this but I suspect' is appropriate. That way, you're not marching in there as if you're the oracle and all your advice is gospel.

Am I an expert at rats? Hmmm....probably not. There is lots I don't know, and I learn something new, be it about health, behaviour, appropriate foods, the right meds, every single day.
But I know a lot. And I get a lot of questions thrown at me, probably 2 or 3 a day. And if Im not sure on something, I will make sure I make this clear that all I'm doing is hypothesising, not stating a fact.

To sum up?
1. ASK, don't assume. If you're not sure of something on a pic of an animal, ASK the owner for clarification first. If your doubts/suspicions are confirmed, THEN give advice. But never assume something about an animal based on one picture.

2. Know your shit before you try to teach someone else theirs. If you are unsure or less knowledgeable in one subject, make that known before you speak, otherwise the person may take your advice without checking it, and end up harming their animal more.

3. PLEASE learn cultural differences. The way some animals are kept/their appearance in the UK is different to the US and I'm tired of having American standards applied to my animals, as if the entire world MUST be American! I make no secret that I'm British, and we do things differently in some situations.
Here, for example, its common to allow cats to free roam, and is, generally, considered cruel to NOT let a healthy cat outside to roam. Some rescues won't even consider you as an adopter unless you can demonstrate that you'll allow your cat outside.
In the USA, it is the other way around, generally. I've had no end of abuse from American cat owners who have grown up with one system, and can't get their head around the fact that it isn't like that here.
We also don't declaw cats, we don't crop our dogs ears and dock their tails, and some breeds are illegal here (pitbulls, anyone? If you are seen with one here, the dog will be seized and probably destroyed, and the owner will be in trouble)
Again, it comes down to the old 'asking vs assuming' thing. If you see something you're not familiar with on an animal picture, do a little research and find out why the animal looks/is kept in this way, and you may discover it is a cultural difference, and not due to the owner being wrong because they're not doing it 'your way'.
Also be aware that some products are just not available in other countries. Trying to advise a USA rat owner and reeling off a load of products that are UK specific is pointless, and vice versa.

4. If you DO happen to be someone who is very knowledgeable and in an acceptable position to advice others, then please heed this: get over yourself a little. Yes, I said it. So many people in the animal world can be so very militant and unbending on so many issues, and will bully the hell out of anyone who is less knowledgeable, or who is doing something 'wrong'. 'Its my way or the highway' very much applies in lots of animal circles.
Now, there are things one can do to a rat that are unarguably incorrect, as in, they will harm the animal. Some things in pet keeping ARE black and white, either right or wrong.
But not everything.
There are many ways and variations in doing things, and just because it doesn't match your system 100%, that doesn't make it wrong.

You may well change YOUR set up or husbandry methods in a year's time. We all learn, develop and adapt new methods as we learn more and settle into owning that animal.
One person may get their rats out for 2 hours of free range, another may only be able to give 45 minutes. Both are fine, to me. One person may not give their rats hammocks because they destroy them, another may swear by their necessity, both are fine to me.
When you're knowledgeable on something, its easy to believe you are the guru and you can do no wrong. But always keep grounded. Of COURSE if something is blatantly harmful to an animal, it needs to change.
But things don't necessarily need to change just because they're not the way YOU do it.
People know their animals better than you know their animals. What works for your rats may not work for theirs.
And we were all beginners once. We've all made mistakes. And I bet we all wish that when we had made those mistakes, there'd been someone there to tell us nicely what we could do to change it, rather than accuse us of being animal abusers.