movement: I'm not suggesting that EEXIST should go away, just that in the case where the new file already maps to the same inode it shouldn't be invoked. If you can think of a specific case in which that wouldn't be the preferred behavior, I'd like to hear about it.One can use stat() and compare the inodes in case of EEXIST, but I'll bet hardly anyone thinks to do that.

link() wouldn't be used in the first place if rename() were implemented atomically like it's supposed to be. Unfortunately, some implementations are broken.

This link explains in detail how maildir works. The lengths which it goes to to get reasonable semantics on top of a file system data store are quite comical. It does one very clever thing though, which is that it encodes data into the file name, forcing new renames to declare the old state as a precondition, thus preventing race conditions where something else modified the file info since it was read.