I can't type comma sign today though I could do it yesterday. It just doesn't appear in any gui app or terminal. I can catch it with xev - it appears not to be hardware problem:
Not sure if it's related but I started to use a new external usb keyboard about a week ago. Current problem is persisted for both this usb keyboard and native laptop one
I would appreciate if someone point the direction to ellaborate
Upd: I could normally type comma in console mode. + If i switch layout the key with same keycode is also not typeable (specifically 'б' in cyrillic layout)