You are right Kate, figuring out how to reply to a known post is a few steps down from clumsy. Wonder if I can hack a bookmarklet (or maybe it exists).
I hand added 500+ sites to an aggregator for ETMOOC; definitely not efficient. In a wide open course, people throw all kind of junk in a form. For a class you might be able to specify that student make a standalone blog (much easier to add to Wordpress automatically). But you do not have that either. I *think* from what UMW is doing setting up a hub is not much work. I think in those cases the inoreader or netvibes approach may be better, though still feeds need to be added.