The problem was introduced when the user rename branch was merged to master but isn't actually related to user rename.
In the old changedigest-notification.vm file, a $page is used. It has been assumed that this was a com.atlassian.confluence.pages.Page object but it isn't. It's actually a com.atlassian.confluence.mail.reports.PageReport and it doesn't have a 'creator' property. This should be changed back to creatorName and lastModifier should be changed by to lastModifierName.
(See lines 20 and 23.)
The recommended e-mails are also affected but instead of showing anonymous they will just show no author at all. I think this will be acceptable for OD customers to receive (it won't spook them into thinking anonymous access is enabled on their site).
The problematic changes in this case are in popular-content.vm:
$contentItem is a com.atlassian.confluence.plugins.dailysummary.content.popular.PopularContentExcerptDto. It doesn't have a 'creator' property. It has a creatorName property instead.
stephen.gramm@nasa.gov I believe that this issue is unrelated to what you are experiencing. My understanding of your issue is that Change in the last 24 hours emails are being sent from Anonymous user in the From: field. This issue deals with the Change in the last 24 hours email body containing pages that were changed by users but listed as changed by Anonymous. To the best of my knowledge, this specific issue occurred in OnDemand and was promptly fixed. It never affected our standalone releases. I think the on going issue you are interested in is: https://jira.atlassian.com/browse/CONF-26159. I will make a comment on this issue separately.