[NOTE: COMPLETELY REVISED WITH ACTUAL USEFUL INFORMATION THIS TIME]
A number of commenters have been getting the error message “”You must be logged in to make
a comment from that address” when they try to comment.
This is because WordPress has made a change to how it handles comments. Here’s their explanation:
Now, if someone tries to comment with an email address that’s attached to a WordPress.com account, they’ll need to sign into WordPress.com before they can comment.
If commenters have forgotten their password they can request a reset:
If you don’t have a WordPress account, this shouldn’t affect you.
You can contact the WordPress people if you’re still having problems. Or, presumably, switch to using a non-Wordpress-linked email. (Which will send you to moderation for your first post.)
Thanks to Viscaria for the info.
EDITED TO ADD: Some people are still having trouble even with new emails/accounts. If anyone has any advice, please let me know. Or contact WordPress at the linky link above.