I did cwCtrl-Ra at the beginning of a word to paste the content of register
a in its place. And this, I thought, is done entering insert mode only once; or at least, never going back to normal mode.
It obviously worked, and I pressed Escape to go back to normal mode.
Then I realized I had picked the wrong register, so I hit u to undo the change.
But this only reverted part of the change, as I had done deiCtrl-Ra or cwEscapeaCtrl-Ra.
I've also verified that
. also only replayed the Ctrl-Ra. Well, not quite because it enters insert mode before doing that.
What is this?