Yeah, I have heard similar accounts from other people! And I agree that it's not people being intentionally clique-ish, they just don't... idk, perceive AO3 as a community they're in where encouraging other creators would be a nice thing to do, even if they are enjoying their works and talking about them anyway? Also, I think there's this kind of idea going around that commenting too effusively on the fanworks of someone you don't know is a massive overstep and invasive/creepy on the scale of celebrities not being able to avoid getting harassed by people who "love" them and their work, which may contribute to people being more reticient with "non-community" members? I guess I don't really know though.