Changing images associated with comments

And I apologize for any confusion on terminology above – I really mean “comments” when I said “posts”

While we do allow gravatar images if the user has them, this issue is not really dealing with that. I believe that the majority of the instances where this is an issue, the users do not have gravatar accounts.

In one instance, I know the incorrect image is tied to an email with a gravatar account, but the email address that the comment was changed to does NOT have a gravatar account.

In another instance, both email accounts involved do not have gravatar accounts at all.

esmi-

I think that we may be talking cross-purposes here, so let me restate the problem so we’re both on the same page.

I have multiple existing comments from an existing site.

People who comment fall into one of several categories:
(1) Registered users/contributors with the site (few) who have avatars set in WordPress for them
(2) Nonregistered users who just post comments. These fall into two sub-categories:
(a) Gravatar users (few)
(b) users with no set avatar, who are automatically issued whatever our site is set for. (Currently “Mystery Man” but we have used computer-generated sets of avatars in the past and may return to this after this issue is resolved.)

Here is an example of a possible problem:

A user posts on the forum. He doesn’t want to use his own email, so for some reason uses the “admin@ourdomain” email address. This automatically uses the avatar associated with the admin account. The content of his message is good, and we want to retain that. So, we either remove the email address in the comment or change it. (Doesn’t seem to matter which one).
Unfortunately, the avatar associated with the admin account remains, even though the email has changed. Obviously, we do not want it to appear to the casual glance as though this was an admin-created comment. How can we change this, while retaining the comment? (For purposes of this example, we’ll say that it already has sub-comments beneath it, so we do not want to delete and recreate it.)

Here is another example issue: One of our regular contributors had made many posts under an old email address. She had an account with our site, and had an avatar set with this email account. She then later got a new email address and updated her profile to have this instead. Her old comments with the old address remained, and kept the old avatar. We then moved our WordPress installation to a new server, keeping all comments, but now all of her old comments with the old avatar use “Mystery Man” instead of the old avatar.
We tried manually editing the old email address in the comments to change it to the new email address (remembering that the new email address IS correctly associated with the avatar), but simply changing the old email address did NOT change the avatar.

There are a few other situations where we have wrong avatars showing up. It was much more obvious when we DID use a generated set of avatars, because in some cases an old user had changed email addresses multiple times, and their comments were now associated with three or more different avatars. That’s part of why we changed to a single avatar for everything (other than Gravatars).

Is there any hope for this situation? Is there ANY way to easily change what avatars are associated with what commentors? (Again, keeping in mind that the vast majority of these people just comment on our site and do not have accounts.)