Membership approval and moderated posts, aside from making more work for someone, only slow down the determined. IIRC, the incident on this forum involved someone with something over 100 posts.
The shame is that one determined individual can ruin it for everyone else. That happened on a popular scanner frequency site. After several hacks by the same individual, the site owner gave up and we lost a great resource.
How would you verify that it isn’t your favourite troll in another guise? ISP number?
Yes, the ISP’s are somewhat of a guide, but by no means foolproof…they change if they are dynamic addresses, and this particular cad is cagey. However, the email address is often what gives the ego behind the intent away; he makes up names that are partly off-colour, grossly off colour, too cute by half, pompous, etc. So far, we have been fairly effective at whacking the mole when it first raises its head, but we do need to sleep and talk to our wives for a few minutes each day…you know…[:D]