I run in to this problem all the time when those pesky Japanese sites do address validation ("全角英数字" etc) and I enter my address:

blah blah 1−2−17

It throws a validation error because Kotoeri automatically chooses a "−" character that the validation script (which is, by the looks of the site, usually) probably is calibrated to Windows input. Maybe this is an edge case, but I fear that slight encoding differences like that would panic a user when trying to log in to their account on a different OS (or even a different version of the OS, since IMEs change quite a bit too)

// @height8