Commands
/nick <player> <nickname>
/unnick <player>
/rnick <player>

Options
chatFormat
Default value: "<%{nickname.%player%}%> %message%"
Changes the message type that appears when a player types in chat.
"%{nickname.%player%}%" is the username of the player.
"%message%" is the message.
This needs to be in quotes!
doNickBroadcasts
Default value: false
When true, if someone changes or removes their nickname, it would display publicly in chat.
Acceptable Values: true, false
By default, all nickname changes will be broadcast to operators, regardless of the value.
usePrefix
This determines whether nicknames will have a prefix at the start of them.
e.g. If a player nicks as "Notch" and this is true, assuming the "prefix" value is "*", it would show as "*Notch" in the tablist and nameplate.
Otherwise it will just show up as "Notch".
Acceptable values: true, false
Default value: true
prefix
Only applies when you have "usePrefix" set to "true".
Default value: "*"
This needs to be in quotes!