I can't even log into my account on there right now, so not exactly feeling great about it. I'm fine with making a new account, but idk if they still allow that.
I didnt see anyone answer your question yet, so I figured I would answer.
I was able to see your posts and comments, and Im from another instance. (saw your post on a different instance and then found this comment)
Posting seems to depend on the instance's rules. Others can you see where you been so I would always assume its public. Good news is that its easy to make multiple accounts (to separate activity), some dont even require an email depending on the instance.