Probably an urban myth but allegedly one of our Cabin Crew was disciplined over this sort of thing. Apparently an amply proportioned gentlemen of dubious hygiene status was oozing onto the seat next to him. The poor soul who was assigned said seat quietly asked the hostie if she could do something at which point fatfuck protested "why, I've paid for my seat, same as him". The response, "yes Sir but he is only getting to use half of it".
Cue righteous indignation, abuse and harshly worded letters etc.
One that definitely isn't was a bloater sat in an exit row seat who the Cabin Manager felt would be unable to operate the exit in the event of a nasty. She asked him politely and discretely if he would move. He loudly and abusively refused. At which point the CM called me and I explained the two options available to him, only one of which involved travelling on the aeroplane.
Again, a letter was sent but thankfully my Base Manager at the time had an IQ bigger than his shoe size so nothing came of it.