ChatLikeMe is a chat format plugin, it contains various values that you can use in your format. Will add more on request.
The config of this plugin can be somewhat confusing sometimes.
So please look here for information: Click me to go to the configuration help!
Any format part that has no value will be removed from the format, so if you have a prefix part in the main format but you don't have a prefix then it won't show it.
Example for this:
I have as format : "{PermissionGroupPrefix}<%s> %s"
If I would have a prefix "Durp" then it would show this: "[Durp]<timtower> Test"
If I don't have a prefix then it would show this: "<timtower> Test"
Probably something that server admins will like, no unneeded parts of the message.
Create a ticket with a request for them, it needs to contain these things: