Diffusion is showing mysterious diffs for commits in which an entire directory is removed. See rP5c1e4488dedafda08684b33a8a4786cf687d2811 for example, in which the `src/infrastructure/daemon/bot` directory was deleted:
{F5090900}
(For rP5c1e4488dedafda08684b33a8a4786cf687d2811, the "diff" shown for `src/infrastructure/daemon/bot` is actually the diff for `src/infrastructure/daemon/bot/PhabricatorBot.php`)
I often see this bug on our Phabricator installation as well.