I wholeheartedly agree with you on that "Anonymous is legion" crap, but having a tripcode does say something about the user, regardless of the supposed 'quality' of posts.
. Let me explain what I mean a little better.
What I'm saying is, when someone's regularly using a tripcode, they're consciously setting up an identity. To them, it's like they're a user in a forum. Their posts are not 'free', sort to speak, in the sense that they're all building blocks in the building of an internet personality.
That's why the same post's 'quality' is different depending on whether it's anonymous or not. If posted anonymously, the user simply wants to get what the post says out there, for others to read, of hell, maybe even for him/herself. But for a tripfag, it's a carefully constructed piece of self-validation, and that's just annoying.