Bribing monsters has some potentially non-intuitive behaviour.
First, if a bribed monster is attacked, all bribed monsters in LOS are turned hostile, in addition to any friendly (but not allied) bribed monsters on other floors. The different behaviour between friendlies and allies is the non-intuitive aspect in this case.
In addition, the game does not warn that attacking bribed monsters will turn other bribed monsters hostile, so this should be mentioned as well, similar to how attacking allies under an ally god will give penance.
Secondly, if a bribe expires, friendly (but not allied) monsters turn neutral. This by itself is not non-intuitive, but attacking a neutral (and formerly bribed) monster will not turn bribed monsters hostile, and similarly, attacking a bribed monster will also not neutral monsters hostile (but it will still make other bribed monsters hostile as described above.)