It depends on what to mean by "rename". If you just change Guest to Visitor then that would not be a problem but if you changed ANONYMOUS to VISITOR then you would have some serious issues with your board.
David Remember: You only know what you know and - you don't know what you don't know! My CDB Contributions | How to install an extension I will not be accepting translations for any of my extensions in Github - please post any translations in the appropriate topic. No support requests via PM or email as they will be ignored
It's an account just like any other but it's the one for everyone who is not logged in so you can control what visitors see. It should be in the guest group on it’s own and cannot be renamed. And yes, if you mess with it you will break your board.