I'd say be very, very careful with the usage of 'derp'. Whilst I'm personally not offended by the word, it is considered ableist and offensive in many, many online communities. It's, by definition, an internet-savvy substitute for the word "retarded" (which *is* undeniably offensive). I've had a fair few friends with mental difficulties go eeriely silent and upset when there's someone harping on about "LOL I'M SUCH A DERP XDDDD" in local. Whilst many people don't intend to use it offensively, it does have offensive connotations-- intentionally or not.