CHANNEL MODE u

Usage: MODE <channel> +|-u
u - Channel user
Sets a user to +u. He/she will be identified with a - in front of the nickname. While adding someone to the UOP list gives them certain abilities, moding them +u does not. However, it can be used as an indicator.
What it would indicate would be up to each channel to decide, a help channel might use it to show a guest helper, a chat channel might use it to show that the person was friends with one of the regulars, but not themselves around and trusted enough to have earned voice or ops.
Privilege: channel operator
Examples:
/mode #movies +u Tessix

CHANNEL MODE U

Usage: MODE <channel> +|-U
U - Channel knocks
When this mode is set and user tries to join the channel but fails due to a ban or other channel mode, it will send a knock to the channel operators telling them that a user is trying to join. This will allow the channel operators to INVITE that user into the channel.
Privilege: channel operator
Examples:
/mode #movies +U