a Fergasun
A Fergasun is when someone starts a thread so dumb it makes your brain shut down, and then he walks away like he’s never coming back.
A person says, "I believe the earth is flat and also a conspiracy." Then he walks away.
A thread that says, "I think the clouds are evil, and the sun is a trap." Then the poster never returns.
A post about why the internet is the worst thing ever, then he leaves forever.