Interestingly, anonymity doesn't reduce the value of chat. It is a chat where anyone can make up their own name and say whatever they like. Nobody (who isn't a total idiot) uses it for secure communication.
Impersonation is possible, but it is always up to the reader, in the end, to choose what to believe. If you see guest_Vatsis and they claim to be Vatsis, you must make your own judgement.
Relevant information:
Chat doesn't have a "log in" function. You just choose a (non-unique) nickname. IPs are visible. Lurkers are invisible.