bug: pressing ]] with text highlighted surrounds text inappropriately and can't be undone

[dbieber]

To reproduce, select text, and press right square bracket twice ]]. You'll end up with ]]text]] which as far as I know is useless, so I think this is a bug. Then, cmd-z does not undo the insertion of the square brackets. This also seems like a bug.

Let me know if you'd like more information.
And maybe this is a "good first issue" too -- just speculating.