Commenting is now restored. I ended up (reluctantly) upgrading to MT3.11, solely for the ability to bulk delete any future spam attacks with ease. But clicking around a bit, I’m noticing some other interesting features, and am now happy to be on the latest version.
A tip on upgrading. If you have a large site with a lot of entries and comments — I’d suggest making sure you’re using a SQL database. I was previously using Berkeley DB, and upgrading those large databases failed every time (timeouts). There are scripts (possibly already there) to transfer from Berkeley DB to SQL. Do this first. The rest of the upgrade process went very smooth, and MT in general looks to be running faster.
I’ll be continuing to add more spam-blocking features to the site now that I’m upgraded. Thanks to all those that have written in with offers to help. Very kind of you.