I can only think of one person off the top of my head, but for me it would be easy to find more since I have a reddit account where I save interesting posts. If you go on other forums, you could just keep the idea in the back of your mind when reading and if there's someone who's really knowledgeable about a subject or has interesting ideas or research, you could invite them or make a note of their username to invite later. Like I said, it doesn't have to be a strict Mensa thing. The main caution is to avoid inviting NPCs from either the left or the right.