I think if we disable pinching while modifier keys are pressed, that should resolve this issue. The basic problem is that command+scroll can easuky get turned into command+pinch and both have a somewhat-similar effect so the user may not realize they ended up doing a pinch instead of a reflow zoom.
Bug 1540988 Comment 9 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
I think if we disable pinching while modifier keys are pressed, that should resolve this issue. The basic problem is that command+scroll can easily get turned into command+pinch and both have a somewhat-similar effect so the user may not realize they ended up doing a pinch instead of a reflow zoom.