Recently I looked at situations where the PostNotices table shows a different OwnerUserId and DeletionUserId. This was based on Glorfindel's advice, who suggested this as a way to find bounties which were cancelled (refunded) by a moderator: When a bounty is returned by moderator, is this shown in the revision history (timeline, SEDE)?
I have run the following query on Mathematics: https://data.stackexchange.com/math/query/1236765/bounties-cancelled-by-moderators When looking in columns with users, sometimes the user shown there an the end of a bounty (i.e., the user who removed the notice) isn't a moderator. Moreover, in those instance the timeline the revision history show the same user - which is different from the information obtained from PostNotices table. In order to make them easier to find, here is a query which is restricted to these instances. The posts in question are: 3465251, 3354783, 2783577, 236640, 2651720, 979747.
I did not find such instances on other sites. (I have to admit that I did not look for many of them. Moreover, it is much easier to notice this on a site I am familiar with, since I know who are present and past moderators.)
EDIT: A moderator on Mathematics Stack Exchange confirmed in chat that some merges have been done.