I've noticed lately (and it's probably just in a few of the circles I travel in, and I don't assume that it's a widespread problem) that many artists are dismissive of their fans who may not draw. They assume that because these people are not artists, their artstic opinions are invalid, and should be dismissed. I honestly think this is terrible, for a number of reasons.
On the internet, it's hard to tell unless someone links ALL of their internet identities, whether or not a person draws or not. They may draw as a hobby in a sketchbook nobody sees, but because it's just a minor hobby to them, they don't feel any need to spam the rest of the world with their doodles. Just because you don't see it, doesn't mean it's not there. They may also function as an artist outside your realm of interest. When I was in highschool, my physics teacher was taking painting courses and completing master studies, aspects of his life he didn't share with the majority of his students. Just because you don't know, you shouldn't cast judgement.
Secondly, unless a fan is making detailed critiques about your artwork or about how you're doing your artistic job, there is no reason their opinion isn't valid.
Some of the best critiques I've ever gotten were from non-artists. People who may not identify as artists today may have taken art classes that've trained their eyes and given them the vocabulary to provide a decent critique. Many artists are too self absorbed or busy to really look at and judge their friends' work, or may make justifications based on style. A non-artsy person is less likely to do that. Yes, I understand that 80% of people have no idea what good art is, but that includes artists as well. There are a lot of people who call themselves artists who don't deserve the title, and quite a few people have been tricked by decent tracers.
If something looks 'off' to a fan and they can tell you WHY, there's no reason to just dismiss their opinion. You have every right to disregard it after due consideration, but you need to treat the people who spend time looking at your artwork with respect. Most of your audience won't be artists, just average joes looking to relax or be stimulated, so if you throw away every opinion by a non artist, you're tossing away your entire audience. This is especially true of mainstream art, where most of the fanbase can't draw for a hill of beans, and particularly true of anime fans, the majority of which consider themselves master artists without ever having taken an anatomy class. I'd rather the fan who is brave enough to be my friend and TELL ME WHERE I AM MESSING UP than the fan who's so busy kissing up they can't find the words to say 'that face is lopsided and awful'.
This doesn't mean you should be stricken when someone leaves a nasty comment on your blog. If a fan takes the time to word something respectfully, at least give it a passing thought.