Editing files on Windows has an annoying habit of making them show up +x on Unix. Windows doesn’t have an idea of an execute bit, so some ambiguity is expected, but still. Turns out the real culprit is the map archive configuration option. It’s on by default, which means the Archive bit in Windows is mapped 1:1 with the U+X bit on Unix. That’s really stupid; Windows apps set the Archive bit willy-nilly (hello, Notepad++) and it gets annoying, particularly with git tracking file modes. So configure Samba with “map archive = no” for your fileshare and life gets better.