It depends on the subforum. The private subforums are not search indexed, but the public ones are. Fortunately the more sensitive subforums (such as the abuse subforum) are private. If you're worried about your username being connected to things, you can ask for a username change in That's So Meta!. In any case, welcome!
This is a new account name, but some of the stuff I'll specifically talk about is about a group that at least 2 members know about. I'd like to give a shoutout to the person who told my friend about this place.
Hello! Without knowing the details of what you want to talk about, I'd say that good bets for a home for you to post about this stuff would be either Is This Abuse? (covers all sorts of abuse topics, the subforum name is just a reference to a regular anon seebs used to hear from on tumblr), or the Holler Closet, found under Brainbent -> Holler Closet (brainbent is public, but the holler closet part of brainbent is private). That subforum became a general spot where lots of people made personal threads for all sorts of reasons, so if you want to have a thread about you and your life that's hidden from google, that's a decent spot for it. (fake edit: ahh, chiomi ninja'd me while I was typing, but I'll still go ahead and hit post)
Note, private forums are still searchable within the forum, but you can't see the "private" forums unless you're logged in.