I'm pretty sure I know who you are now
What do you plan to do with that knowledge?
I'm going to do something that I shouldn't.
If someone wants to keep their identity hidden, it's rude to try to pry and find out who that person is. You should be respectful of other people's need of privacy as they could have good reasons for wanting to keep anonymous.
I just want to know who you are.
I can understand that you're curious about my identity. But finding that information without my consent is very offputting. When gaining information about people you should just simply have a conversation with them and ask questions.