To get irritated with MNs who have very long nickcnames with peculiar spellings. I like to say Hi to the person I am "talking" to especially when there are a lot of people on the same thread, but I get fed up of really long ones eg. Ilikeorangesbutdontlikelemons - I made that one up and it's easy enough to just call her "Oranges&Lemons" but sometimes there are wierd ones that are long with peculiar spellings too, and no easy to shorten.