Pablo Message received.
About 'fakers', the site is by nature an anonymous chat site. People posing as other people will happen from time to time, which is exactly why tripcodes exist. As far as I know, the developers love anonymity and likely won't consider restrictions on any names, especially since some of them are the names of anime characters.
If a user is faced with a situation in which another user is incessantly logging in using their or their friends name, for the sheer purpose of getting under there skin, the user has a few options. The first and easiest option is, of course, getting a tripcode. The user must: a) Choose and keep a tripcode--- Do not change the password for it, because it defeats the purpose. If the user decides to change their tripcode, they should tell their friends. b) Talk to all of their friends and have them memorize or write down the tripcode, then keep their eyes peeled for the impostor. c) Do not share the password. The public tripcode that people see in the chat/after login is the one the user should be sharing with their friends.
The other option, which by all means, a user can do both, is: Gather some screenshots to show what this user is doing. Create a report on this user via e-mail, and send it to firstname.lastname@example.org. Be as detailed as possible. It could help to tell us when, and how often this user is doing these things. Tell us which tripcode is their own, so that we don't have any mix-ups. Us moderators can not only try to find out who it is, but we can see how often this person has been doing it to confirm the report. If the situation is clearly harassment, we can place a ban on that IP address.
Here is a third option which should be obvious: Have the host use the Ban & Report option every time this user logs on. Ignore them, they will grow bored and drift away.
I am a little confused about your suggestion regarding the "Roleplay button", you can feel free to explain further, but so far it sounds like it may possibly be counter-intuitive.