This is a B2TR bug-bear of mine (I can't remember whether or not it was a problem in plain B2).

I'm typing away, powering through some work, and then I need to make a change. Say, I think of a word that better expresses what I'm trying to convey. So I hit undo (ctrl+Z because I'm working on the keyboard) and start to continue typing.

Not so fast. Undo hasn't undone. Or at least not completely. It's canceled the last letter I typed. I hit undo again and another letter disappears. Not such a problem when I want to replace "talk" with "presentation", but when it's the other way around, it's a real pain.