Sometimes when I'm browsing on other message boards (like Straight Dope), some poster will quote from a previous post, and underneath will write a single word: "This." This what?? What on earth does that mean?

This

It pretty much means "I second this".

Just messing with ya!

I think when the poster post "this"....it is in agreement with what the previous poster said.

Wow, you're fast. I get three replies before I even leave the site! Thanks

+1 is another one you will see.

And QFT (quoted for truth).

very funny

This