I've seen recently that this new feature had been added to GAG. So I expected that, when a user posts a private comment, only he and the asker could see it. However, I've seen on someone's user page that the asker's replies to a comment were visible. I mean, it isn't visible from the page of the question, but through the user's history. Is this normal? Isn't it supposed to be fully hidden to others?
Nah, you're not the only one to notice this issue. I've seen other users' private opinions listed on your page just like you and many others. That is a problem since the comments aren't really private. It's kind of funny to me, though, because you can see if the person was being a perv on all those "How Do I Look?" questions. That shows me that private opinions can promote creepiness... not good.