"He was most annoyed when I empted his deleted emails without thinking, but had to admit that it was entirely his fault for having such a non-standard workflow."
Back in the days that a 250MB disk drive cost what I paid for my first house, I used to set up a daily job to delete compiler and utility listings with a file extension of ".LIS" or ".LST", and various others which denoted temporary files which both took up lots of space and could be easily regenerated.
Along comes the user who thinks that he's above naming conventions and was writing memos with those extensions.
I managed to survive his complaints to management with ease, and rub his nose in it at the same time.
He was one of life's back stabbers, so justice was done :-)