Emacs (on Mac OS) font size kept changing on me. I finally figured out what was causing it.
CTRL-OPT + two-finger swipe up/down
And the status line, where it shows the file type, actually shows +1, +2, etc when the font size increases by one or two steps, etc.
This was driving me crazy. I'm going to blame this, like everything else, on the enormous trackpad.
