[myron]

1) yes, it does, but only if the movie is not existent in DB. We don't do an "update" from NFO here.
Basically, because TMM is designed to be small and simple, and defining of "master owners" for every metadata is kinda unmanageable/-configureable.
So for the watched flag, we use trakt.tv, which can sync just these things pretty well....

2) on every change to relevant metadata, we automatically rewrite the NFO (eg after scraping); and on pressing OK in edit screen.