IAT doesn't work correctly with Orion editor in XUL (stylish)

Platform: Firefox 22b1, source Ubuntu official ~mozillateam (https://launchpad.net/~mozillateam/+archive/firefox-next), Ubuntu 12.10 amd64

IAT seems to work at least partially, insofar as I can tap the "edit" hover, change the contents of a text file in an external editor, save, and get the changed contents back in a text field. However, the temp file hangs out there after it's been closed in the editor, and seems to survive browser restarts (warm restart, cold start to new session, etc.).

This is screwing with Stylish something fierce, and I nearly lost a very complex userstyle to it. I'm using Sublime Text 2 ( http://www.sublimetext.com/dev ) for amd64 Linux. Don't know if that's related. fuser reports no file locks remaining after Sublime closes the file.