sometime you need to vent, you need to talk about how you are currently feeling, not how someone else thinks it would be better for you to feel.

I understand that, and I wouldn't have a problem with that sort of thing. But a lot of the posts on this particular community aren't just venting; they're people looking for encouragement in self-harm, and getting it. Stuff like this, for instance; several more links from here.

It's the difference between "I want to be thinner" and "help me fast".