...the moderator delegated limited powers to the initiator only of a given thread? Eg:
1. the power to warn a poster that the tone or content of his or her posts is not welcome, which you can do anyway, but the tiger would not be toothless because
2. you have the power to lock out a particular poster for stated cause and
3. you have the power to lock down the thread for stated cause.
I think a trial period would be fun. Some might fear abusers getting drunk on power but I think any abuser will only make themselves look worse, so it would be counterproductive. The vast majority of us want at least to look responsible.
I don't know how sophisticated the software is but perhaps the recipient of a warning as in point 1 above would have a symbol on any subsequent posts in that thread, eg a tomato-splat, or a flat tyre, or a...hmm, I think I had better post this now before I get carried away.