by penny-arcade forum members it is to be used in ways that make no sense
Rather than using "meh" to show indifference they use it to imply the extreme opposite in an argument, negative emotion, or complete disapproval.
Also in some cases it is used to make ones self feel cool
. Possibly validating ones meager existence.
1: (in responce to being told a joke)
"Meh, that's the worst joke I ever heard in my entire life."
note: the user of the term has opened up the sentence with "meh"(which denotes a lack of opinion) but finished with an extreme posistion on the joke, thereby defining themselves as an ignoramus.