J,
[Renaming the "old" one] seems like a big loophole around Mark's
intention of not allowing reuse of a group name for a significant
period of time after a group has been closed.
I think it is a desired feature more than a loophole.
If a group wants to rename itself yet block access to their old name they can always create a new group under the old name. In fact I'd usually advise doing that as a place to hang a "We've moved" notice.
An even better feature would be if the rename reserved the old name for a limited time (a day maybe), making it available during that time only to the user that performed rename. That way there wouldn't be any "window of opportunity" for someone else to swoop in and take the name.
Shal
Shal Farley