I was just perusing about on main, when I inadvertently pressed the i key on my keyboard. This is what happened:
i.e. my inbox popped up, with fancy number-key shortcuts to access inbox items (style very reminiscent of old text-based RPGs). I started pressing other letters and more things happened that I had never seen before. I have never touched any sort of keyboard settings or anything of the like, to my knowledge, so it seems these are built-in (?).
Can someone point me to some sort of documentation on this?