Going through my Collection, I discovered I'd mistakenly marked 4 of my DVDs as Watched so I decided to delete the History Events for those 4 DVDs in an effort to correct my mistake.  But while deleting these events may have removed the number of times watched, they still show up in the 'Watched By' list with the mistaken dates I thought I'd deleted.  How can I remove the entries from the Watched By list?  And why didn't deleting the History Events remove the Watched By enties anyway?

"watched by" isn't as carefully implemented as other features. I once reported that when you delete a collection item, its "watched by" event(s) continue to exist. These show as empty names in the history list of a user. To date, I haven't seen this repared as in listed on the 'fixed bugs' list, though I think I didn't check the latest release on this for repairs.