Do people regard it as wrong these days to drop the full stops in P.S.? We are asked to write as correctly as we know here, and until today I've always put the full stops, but they look and feel very fussy to me, particularly on the web, for some reason. My practice, I think, is in an email to put PS. The full stop not to mark an abbreviation, but the end of an (albeit short) sentence. In a letter, I'd probably put P.S. still. I'm very tempted here to put PS., but that seems to run against our formal instructions. What do people feel?