"Critics are like eunuchs in a harem; they know how it's done, they've seen it done every day, but they're unable to do it themselves."
- Brendan Francis Behan

You didn't mention that personal preference =/= valid criticism, like the million times people tell artists the characters are the wrong gender or their genitalia are too small or too big etc. under the assumption that it's a constructive comment.

After a certain point, all critique boils down to the opinions of the person writing it, and it can be useful to hear what people do and don't like.

These people aren't talking about the art at all, however, they're talking about themselves: what they want and what they like. When someone says "more giant black roosters, please" what they're saying about themselves is "I don't care about your work, I have the mind of a march hare, and i expect you to give me what I want." They shouldn't be writing comments, they should be writing cheques to the sort of artist who are willing to take such things.

I disagree on the first bit; a good, constructive critique is an objective review of a piece of artwork.
While it's nice to hear if people like your work, it's not especially important to an artist if the viewer doesn't like the work for subjective, personal reasons. It just means they're not in that artist's target audience.
Especially in regards to people stating an alternative preference when it comes to commissioned work.

"It just means they're not in that artist's target audience."
I get what you're saying here. I ink manually, using india ink and nib pens: if someone says, "inking in flash is way better," they really should go find someone who inks using flash instead of pestering me.

There are times when subjective opinions can be very useful, especially if they're from an audience that you do relate to, or from someone you trust. On the other hand, an outside opinion can help a lot if an artist is stuck in a rut, feels like their work is stagnating, or is looking for a new direction to improve in.

The problem is when someone is rude, overbearing, or refuses to back down when their opinions are declined. That's not subjectivity, that's arrogance.

"Especially in regards to people stating an alternative preference when it comes to commissioned work."
I'll agree with you on that one. Some things are not for sale, and commissioning an artist does mean having to respect their work. This isn't McDonalds: artists don't have to remake something a hundred times just because the client throws a hissy fit, and sometimes you don't get a full refund. There's a reason for all the protocol, like downpayments and sketch reviews and such.

Nah, I mean a third party commenting on a commission drawn for and paid by someone else; the customer wanted a flat-chested character for example and someone else goes "needs bigger titties" and presents their opinion as fact when really, if the customer and artist are content, is a moot point.

As for the value of subjective opinions, I'm more referring to the drive-by "You should draw more dudes"-type of comment, or whatever that person's personal preference is when he/she is not even invested enough in a person's work to +watch them for example.

Ah... comments like those are just grade-A tripe.

What about elements of art that are telling a story?

Some art has a story to it that is just as important as the picture. Yet I don't know if the same applies totally to a story element to art.

Is it even wise to try constructive criticism to the story? In at least one case I say what I see in the story and the impressions I get from it. She seemed absolutely thrilled about what I thought about what I wrote to her.

A picture, a story, and an idea. Are they really that different from each other other than the obvious?

I would say that anything about a piece of work that makes you react is worth commenting on. That goes for writing or visual art, and music as well. Whatever that reaction is, the person who made the work will probably benefit from hearing it.

I primarily do comics as an artist, and the writing is just as important to me as the art. I appreciate comments on both aspects. When I write critique, even for something that isn't a comic, the storytelling elements are still important to me. I see artists who have very refined inking, or know their anatomy inside and out, but their facial expressions and body language are really flat (which I would consider storytelling elements), and I'm bored. When I see novice artists post work that has some feeling to it , it's top on my list of things to mention. In part because it's encouraging, but mostly because I don't want them to lose it down the road.

For the first draft of HTTTA pt.1, I tried to word everything so it wasn't specific to visual art. Constantly referring to "the work" or "a piece" sounded super-pretentious, which I wanted to avoid as much as possible. Personally, I consider writing to be "art" just as much as drawing is.

A-frickin'-MEN....

Critics are traditionally giant pricks. This isn't helpful. It's not necessary. But scathing criticism is unfortunately fun to write and humorous for others to read, so people do it anyway.

I don't. I have a philosophy.
"The mediocre teacher tells. The good teacher explains. The superior teacher demonstrates. The great teacher inspires.” -William Arthur Ward

When you offer critique, you are a teacher. We are all teaching and learning from each other constantly. I very, very rarely critique artwork; I'm much more often asked for advice about life in general. But when I offer my advice, I do my best to offer it in such a way that I hold with that philosophy... and I don't settle for mediocrity in ANYTHING I do.