PhD Historian pointed out to me that some of the comments he had submitted hadn't been showing up and so I went in and found a lot of comments awaiting approval that I hadn't received the email notification for. (I have it set for Blogger to send me an email when a comment is submitted and then again when I approve it so I know it went through.) I'm not sure what happened, but I've set it up again with another of my email addresses and I'll keep an eye out on the Blogger dashboard as well.
Sorry to everyone who submitted a comment in the last few weeks and are just now seeing it show up! I'm hoping I didn't miss any legit comments in the sea of spam comments, so if something you submitted in the last month didn't post, try it again.
Thanks for your understanding!
** Update July 30 **
Looks like it's working again, finally! When I first was made aware of the problem I went over to the Blogger forums and found a lot of people having the same problem. Blogger posted about the problem and hasn't officially closed out thread (which would mean it should be fixed) but I tried something someone else in the thread suggested and it seems to be working. I'll keep manually checking for comments awaiting moderation for a while, just in case!