Just checked in a change to undelete functionality:
short description: RC now acts like Thunderbird
long description: If you have one message selected pressing delete(key or icon) toggles the deleted status of that message and goes to the next message.
If you have multiple messages selected it will undelete them if and only if they are all marked as deleted. If any one of them is not deleted it will mark those messages as deleted and ignore all of the already deleted messages.
This is different than Outlook/OE which never undeletes with the delete key. The thing is that with those clients you have a right-click menu that allows you to undelete. When RC gets a right-click menu, I would think that it might be preferable to put undelete there rather than following Thunderbird behavior. Or of course it could be an option.
This patch also fixes some weirdness with being unable to toggle seen/unseen after marking a message as deleted.
It also cuts down on the huge number of Javascript warnings that this https://addons.mozilla.org/firefox/1815/ was reporting. I recommend that extension to anyone trying to debug javascript by the way.
-Charles