U choose not to accept "guest" postings, which is all right, but them you have to delete members that don't use their clear names as well, because you can simply subscribe with a phantasy name and continue the habit of anonymous posting nad offending!
Look at the last 10 registered users and u see what I mean

Proposal:
Either accept "guests" or to "check" the list and a confirmation would be required to see if the given email address is valid.
Greetinx from winter-cold Dortmund, Gemany
Ingo Zachos