Blogspot Still Eating Comments

Apparently they're aware of the problem:

We're investigating reports of users not being able to comment on IE8/9 from the embedded form. We hope to have a fix out shortly, but in the meantime we encourage admins to switch to either the full-page or pop-up forms which should be working without issue.

Thanks for your patience, and we'll make sure to update this post as soon as we have more info.

I have made the change they recommend.