0.9.x doesn't have that code, you are probably on master. Try doing a git pull.
Bug with auth when change setting in Mentions
When I set this option in mention plugin, users can't auth on forum if his username have space symbol (example: Brad Pitt), hi can auth only if using the character - instead of a space (example: Brad-Pitt).
So if I set default setting "as written" users can auth use username with space and without character -.