Mystery Man - the default Gravatar

I just had a problem with my own gravatar not showing up on my own site for the comments I wrote. First I thought that clearing the browser cache would solve everything. I was wrong. After clearing the cache, deleting cookies and checking my gravatar (http://en.gravatar.com/site/check/), I was really out of (quick) ideas. Then it suddenly hit me: a few days ago I changed a few things in my Blog’s user accounts. I added new accounts with different user rights and merged the old accounts with the new ones.

After having a look at WordPress’s gravatar code (wp-includes/pluggable.php), everything was clear: WordPress actually pulls the user id and gets the email address which is stored in the user account data for this id. This ensures that if a user changes the email address in the user account, it will always pull the new gravatar associated with the new email address. The user id – for registered users – is stored in the comments table for each and every comment.

That said, if you change user accounts and a user id changes, you need to run

UPDATE wp_comments SET user_id = new_user_id WHERE user_id = old_user_id

otherwise you’re going to have a lot comments from the mystery man…