we know some players play both doubles, e.g. LYD (KOR) and YY (CHN). this year we see chole M (IRL) unusually doubled up for WS and XD. the last time i remember was then the world WS No 1 and 2, Li Lingwei and Han Aiping doubled up for WD with some successes. Does anyone know that the tripled up been done before? i.e. single and 2x doubles.
OOoo... that's a tough one. usually for big powerhouses that is rare as they have so many players they don't need to stretch players thin. we need to look into smaller countries. i remember Wang Chen played WS / WD before for Hong Kong. but i don't remember her playing mixed in major events.
there are quite a number of players who played all three events but from my memory, not in a single tournament. Former doubles great, Park Joo Bong used to win many major tournaments playing both doubles events, and was also quite a formidable singles player when called upon in team events. Maybe someone who will more likely to have done so in a single tournament would probably in the regional games like SEA games, Commonwealth games, etc.
oh and of course the legendary Ra Kyung Min was a singles player before and have played competitively. however, she later on started focusing on the doubles disciplines.
I think that tripled up is pretty common in junior events. Not once they step up onto the senior stage though. I can recall Pisit Poodchalat (THA) being put in 3 events for the AJC last year.