This is a trivial yet annoying issue: I use a mac. While developing, my left thumb is always on Cmd key (as most inspections are invoked on Cmd+<some key or click>). But in conjunction with an apple magic mouse or the trackpad, the gesture of two fingers moving is interpreted as zoom, and so IntelliJ immediately changes ALL the font up/down.
This is annoying and I haven't found a way to disable this. I've also disabled all gestures from Apple's System Preferences but this problem continues hinting that it's an intelliJ issue.