WordPress.com made a change to how comments work last week. This is causing problems for some people trying to leave comments on WordPress.com blogs and is getting a stream of complaints. I have gotten a few messages from people about this issue myself.
In the grand WordPress.com tradition, no mention of this change to comments was made before it started causing problems, and since then it has been getting little or no visible attention from what passes for support. They might want to look into some ideas on that front.
Anyway, it seems that if you have ever made an account at WordPress.com or any of its affiliated services, such as Gravatar, the email address you used has been stored away somewhere and you are now required to log into WordPress.com if you enter an email address that matches one in the database.
Even if you have since attempted to delete your account.
You can enter your email address in the lost password page at WordPress.com to see if you have an address that has been assimilated into the database.
Since I do not actually check the email addresses people use, unless somebody asks me to contact them, feel free to make up a fake email address to comment. I won’t mind and would rather have your comment than an accurate email address.
I will enable anonymous comments in the mean time. I don’t mind anonymous comments, but for some reason the need to enter an email address makes some people behave better.