My brother, who unfortunately is a frequent visitor to 4Chan, tends to go "DERP" or "HERP DERP" at people when they've said something really stupid or exhibited some kind of physical "fail" i.e. tripping spectacularly, running into a wall etc. It is definitely not said with fondness (in fact, it's said pretty much exactly like a 9 year old of my youth would have said "HURR DURR"), and I generally consider him a good guide to "common internet usage," so. I'd definitely say less "you're a dork, aww" and more "I am making fun of people with developmental disabilities" for sure.

/anecdata