Many times on a trip I have been tempted to ask the ATCO if they are a member and what their handle is...
A few months ago I did hear another pilot on frequency ask the FISO (an ATCO on his day off) if he was "the guy on PPRuNe" or similar, the handle was mentioned in the subsequent exchange. Not too hard to guess though as it was Old Warden and there had been a PPRuNe thread regard procedures for event shortly before.
MC.