There is no feedback about a failed GIT commit at all. No status bar message, no status window message, no message in Help->Debug Messages and no error dialog.

At least one the above should happen to tell the user that the commit did not happen. IMO there should be a message in Help->Debug Messages at the very least but also some more visible feedback to the user like an error dialog or at least a status bar message.

The only trace you get is the GIT error output on stderr but I guess most people won't want Geany's stderr regularly :).