An aesthetic issue with the passwd_timeout feature: if PAM decides to chat to the user after they fail typing their password (e.g. if pam_insult is used 😉), the output could be nicer:

[sudo: authenticate] Password: [sudo] Did you forget your password or just your brain?
sudo-rs: timed out

I'm not sure this is a trivial fix and it's not a showstopper in any way (for now). Maybe also @MggMuggins wants to have a first stab at this.