UPDATE 6Jul2010 12:00 noon: Comments seem to be working again, although comment counts on some posts, including this one, are inaccurate.
UPDATE 8Jul2010 6:50pm: Comments are working!!
I've noticed that my own comments to my serpentine post are not showing up on the post, although I'm getting email notifications about them (I've posted 3 or 4 that I can't see). The email notifications give me the content of my comments, so I know I made them!
I've also noticed this on at least one other blog I commented on (Geotripper); my comment didn't show up, or at least I can't see it.
And at least one other Blogger blog today isn't showing a particular comment if you click on the blog post heading, and only shows the comment if you click on comments directly. (This seems to work for one of my comments on my serpentine post, also, but not for 3 others that I've made so far.)
The point of this little post: If you think your comments aren't getting through, please send me an email (not that I'll be able to post the comment for you, but at least I'll know what you've said and can reply by email). It's likely that I'll see your comments in my email notifications from Blogger, but I'm not sure about that.
Also, I'll be on the road and don't have time this morning to set up a "Something's Not Working" complaint at Blogger/Google. I've searched their help forums; so far there aren't any answers, and there may be 1 or 2 people awaiting solutions to the same or similar problems. And it may be a Known Issue; they seem to have a lot of Outstanding Known Issues.
UPDATE 6July2010 9:00am: At least one of my comments not using my Blogger profile but using name/URL is readable to me if I click directly on comments rather than on the post title. It also has shown up on my comment widget. So far, a second name/URL comment of mine hasn't. So something is quite erratic.
UPDATE 6July2010 9:24am: All the comments may now be suddenly showing up, all at once. Don't know if it's fixed completely. Time will tell.