I noticed that a couple of months ago a user reported the same issue I am experiencing on my server and you blew them off and said it wasn't possible.  I assure you it is very much possible and still occuring. I am removing the plugin until it is resolved.

When one player uses any command it changes that setting for the entire server. Every command, Every time, ,Every player. You can say it isn't possible....but I can assure you it is.

I just checked the code and agree that this is possible. The plugin is using a single object to store the default settings, which in some cases can be assigned to multiple players at the same time. The plugin will need to be updated to create a new settings object when players using the defaults want to change their settings.

Fixed in latest version