Don't forget to launch any secondary instances of mutt with -R, or you'll encounter conflicts.

I've been searching for the right way to launch the editor in a new tmux pane, although apparently getting that to work smoothly would take a patching effort.

I launch innumerable copies of mutt without -R, and have never had any conflicts.

Like the original poster, I'm using offlineimap and maildir's entirely.

What kind of conflicts do you get?

Default / typical behavior is for mutt to update the mailbox message state (new, unread, read, replied) when closing the mailbox. Using the -R flag prevents this behavior.

Forgetting to do so is more an annoyance than an End of the World Event, but it's an annoyance which can be avoided with a really simple flag use.

It's something I read when I was getting started with mutt.

Perhaps is much less of a deal than I thought, after giving a cursory Google I can't seem to find what I read that gave me that impression and I don't see any major warnings not to.