Nicknames are limited to 16 characters as this is the maximum allowed above player heads (yes this can be upped to 48 with scoreboards but I chose not to add this for better plugin compatibility).
If showing AFK status above player head is enabled and a player's username/nickname is longer than 10 characters, their nicknames will be truncated to 9 characters due to limitation above.
Player will flicker for ~2 ticks when their AFK status or nickname changes.
Compatibility
This plugin doesn't touch scoreboards, so any plugins using that should work fine.
Probably not compatible with other mods which inject data into Play.Server.PLAYER_INFO packets or depend on those packets not being sent randomly.
Commands
/nick [nickname]: Set your own nickname.
/nonick: Remove your own nickname.
/nicklist: List users and their nicknames.
/afk: Toggle your AFK status.
/setothernick [player] [nickname]: Set the nickname of another player. Needs OP (or permission node).
/delothernick [player]: Remove the nickname of another player. Needs OP (or permission node).
/nickafkreload: Reload plugin configuration file. Needs OP (or permission node).