After a few weeks, please give us a second chance. As you said, the moderators can't really moderate the thumbs. The only thing you guys can really do is take the thumb comments away in response. But there is a middle ground between doing nothing and permanently removing the feature. The offenders now know what they will do has consequences, consequences that will hurt the forum as a whole. Their shadow forum has been brought to light. Perhaps this is enough to get them to self-police.
If it isn't, then nuke the comments.
But give folks a second chance. The benefits outlined by SVB warrant that, and unless a lot of coding is involved to allow comments (and then remove them again if necessary), I can't see any real harm or cost.
I only really post in MC and GC (and occasionally DT ), where the comments, especially in MC, have been very helpful. Perhaps some truly evil things were being said in SW&D, things bad enough that you guys don't want to risk them being said again. Regardless, please at least consider the possibility of returning comments to us in a week or so.
Dredd let Rob Schneider's character live, and that worked out well for Dredd.