In Chapter 32, Professor Sinister enters what Enoby has already stated is Professor Trevolry's Classroom ("I got out of the hole n it was bak in the pensive in professor trevolry's classroom."). However, Professor Sinister then goes on to claim ownership of the classroom ('sinister came in. "hey dis is my classroom wait wtf enoby what da hell r u doing?"'). I think this, coupled with the information that we acquired earlier, would make Professor Sinister the same person as Professor Trevolry.