Now, I could be a be misunderstanding your situation / request. Yet it seems like your looking for (at least in part) to create 'a forum message / topic approval workflow'.
Which could delay the publishing (<i>display</i>) of a forum message / topic until the site administrator approves the message and it's contents.
Reading a little deeper into your message it seems as though you might really be looking for a workflow which allows the user who posted the message to approve their own message via email. This may take a bit more custom workflow programing, but is an interesting idea.
Your desire to avoid requiring users to register might also be another additional dependency which would require an amount of custom workflow programing.
You are correct regarding the part where the user him/herself "approve" their own message (they actually confirm/"approve" their own email).
I'll look into the workflow part, a good advice. I only have limited experience with ezPublish and it sounds pretty tricky... -so if you (or someone else) have any other ideas, please let me know :)