Do you care who it is who's commenting on your writing?
I never have, and have always had a hard time understanding people who react negatively (and sometimes obnoxiously) when they get feedback from someone they don't personally know, or someone who's not a writer, or someone who otherwise doesn't have whatever qualifications they feel someone must have in order to comment.
To me, any constructive criticism is data and it's all useful. Even if I examine it and end up deciding that the commenter simply isn't a member of my target audience (someone who thinks I should get rid of the romance in what's clearly a romance novel, for example [cough]) and decide not to act on the expressed opinion, I now have a bit more information about reader views and tastes than I did before.
Comments are either useful or not, in and of themselves, independent of who's making them. A well-stated and reasoned comment, which clearly has some knowledge of craftsmanship behind it and which refers specifically to a line or paragraph or other specific chunk of a particular story of mine is always worth getting, even if it's written by someone who's "just" a reader, or a stranger, or a nonymouse. On the other hand, if one of my very favorite writers in all the world said, "Seriously, this needs some work," I'd probably thank them for taking the time to comment, but wouldn't value the feedback very much because, wow, vague. :/
Some writers get personally offended when someone offers concrit to a story which has already been published. I don't get this either, because pretty much any mistake I made once, I might well make again and hearing about it even after the fact lets me make a note of it and take care not to make it again next time, even if I can't edit the story which was just published. Learning from my earlier mistakes is always desirable, and I honestly don't care who it is who points me toward the lesson.
Maybe it helps that I "grew up" as a writer in some fairly intense workshop environments. When you get serious pros and intense hopefuls all in the same bucket and have them tearing apart each other's stuff, with the idea that it's better for your workshop peers to spot something than that editor you're hoping will offer you a contract, you learn pretty quickly that concrit is gold and that excessive ego does nothing but block you from any hope of being published. (And in all honesty, the old GEnie SFRT was not for the faint of heart nor the thin of skin, whether you were in the workshops or not.) I grew an adamantium hide in the early years of my online participation as a writer, and while I'll admit that's an advantage which not everyone has, I can only suggest that anyone who wants to be a professional writer grow one of their own as quickly as they can manage. This is not a good business for the delicate or sensitive to be in.
Maybe it's the fact that I value my writing, my skill and my hope of improving both, much more highly than I value the delicacy of my writerly feelings. Sure, I wince for a moment if someone says they didn't care for one of my stories, and I get horribly embarassed if someone points out an obvious flaw I missed. But I want to learn and grow as a writer more than I want to avoid those wincing embarassments, by a few orders of magnitude. I want to know what people think and why, and what they think is problematic or just plain wrong, and the why of that too.
Anyone who can clearly explain what they liked and disliked, what they thought was going on and what they thought was going to happen next, where they laughed or winced or gasped, where I fooled them and where they saw right through my attempted misdirection, what they think worked or didn't work with specific examples and reasons for it all -- anyone who gives me that kind of feedback is going to be one of my favorite people ever, and I don't care who it is or whether I know them or whether they're a writer or whether they're someone who wandered by and posted anonymously. It's the data I value, not the source. Good, clear, useful data is always valuable and always makes itself obvious; I don't need an attached name or title or resume to help me decide whether the data is useful.
Or at least, that's how I see it. How about you?