Me and my friend are making a website which has a chat room on it. However since we do not have access to servers, and thus cannot use php or other languages used to make profile systems, the closest we can come is having a prompt appear to ask for a nickname, which can be changed to anything at any time. However this had lead to abuse.
Recently a rather odd group appeared calling themselves a "cult" that apparently surrounds me since im the owner of the site (Don't question it I guess?). They are constantly impersonating me and other important testers/mods on the chat to spread misinformation and lies across the site. On top of that they are saying "not so clean" things under our names too. It is getting extremely annoying and is hurting the reputation of our site. As a result I was forced to bring down 2 major parts of our site, the chat, and one of our popular games that had the same nickname prompt for awhile, they are up now because we have an active NSFW filter running. However we still have the impersonation problem.
Unfortunately due to the previously stated problem with the profile systems, We don't exactly have a system to identify moderators or admins officially. Our best course of action (Without the profile systems) to punish people is just to prevent the username that was punished from being able to be used as a username by filtering it.
How do I deal with this or make it so people can't have the same usernames as somebody else so that I can bring parts of the site up again? This is a very bad problem so I would prefer a solution that isn't able to be bypassed in two minutes please.