I just made a small modification on your mod so that currently only players with administrative permission can see the private messages of the clans. Otherwise, if this plugin is enabled for everyone from F1, they will be able to see as many public messages as the clans' messages.

Please do not share modified or random versions of plugins directly in forum threads if you are not the author or maintainer, thanks. If you are interested in contributing, please reach out to the currently maintainer else submit a "Patch" if they have that functionality enabled.

I've released an update to add support for team chat and updated using new arguments for OnPlayerChat.