I have reports from registered users of my blog who use IE6 -- they have Avatars and everything -- who tell me when they try to login and post a comment while I have "Users must be registered and logged in to comment" turned on in my Admin panel that they are unable to post a comment.
Here's what one user said to me in email -- username is deleted for privacy:
"I keep seeing the 'you must be logged in to post' message, yet I’m logged in to wordpress.com. Clicking on the link doesn’t help. It takes me to the wordpress login area, but always says welcome back XXXXXX [deleted for privacy] – so I am logged in.
That user told me WordPress.com support said the problem was with IE6 and to not user that browser.
Are you seeing anything like that on your site where IE6 users can't post a comment if you require them to be logged in first?
I know we hate IE6, but some businesses still require their employees to use it and I hate losing comments because of a browser some readers are forced to use because of work or economic circumstance.
Can you test this on your blog to see if you can confirm this?