It marks every thread read up until the timestamp in the last post in the thread. Because of the way it works, triggering the mark read in a different thread would screw up posts in threads that were newer - hence it is only in the newest thread.
Willful ignorance of science is not commendable. Refusing to learn the difference between a credible source and a shill is criminally stupid.
Very cool. Shades of Beavis & Butthead? I'm excited about the new box set, but I wish they'd be complete seasons as opposed to specific episodes. As soon as I know what's included or taken away from the PSP versions, I'll decide what version to pick up.