This is an annoying niggle. There’s bound to be a simple GreaseMonkey et al solution to this – I just haven’t searched yet.
My example: Discourse, GMail, etc have similar keyboard shortcuts. The letter U takes you up/back from where you are. But not Twitter. Nope. It mutes the user, making you scramble to unmute them via the toast before it fades away. At least a few times/week.