One solution if that happens again and more often would be to ask any person wanting to post as 'GUEST, mudcatter's name' for the password to use that name. However, even that wouldn't be perfect. For example, the person posting as 'GUEST,Sorcha' above in that case could have posted as 'GUEST, S0rcha' and with the size of the second character adjusted it would look quite convincing, for there are only minor differences between an 'oh' and a 'zero'. Best perhaps is to hope that this nastiness dies out.

Wolfgang