One of the most commonly used acronyms against disliked comments. So common that a button was created for every comment so that users could express their dislike for a comment even if buried deep inside a long thread.
"Only faggots use the stfu button" - JamesTKirk
In case you didn't know, stfu is an acronym for "shut the fuck up."
But you already knew that, didn't you, so why are you even reading this page?