Scnr

"scnr" is an abbreviation for "Sorry, could not resist." and is used in situations when someone knows that something they do/say/write etc. will probably cause (mental or expressed) negative reactions, but even though the person knows this in advance, they go through with their action because they don't want to miss the opportunity to make a joke, to say something that needed to be said sometime, to say something in a place where it does not belong but that can serve as an effective means of conveying the information. And so forth.