On 2023-04-19 I added a "performs as" relationship to an artist. Two days later the editor who added the artist apparently deleted their account and all their edits were cancelled, seemingly bypassing the check whether an entity is used:
https://musicbrainz.org/edit/98916596
https://musicbrainz.org/user/Deleted%20Editor%20%232381921/edits

Another example
https://musicbrainz.org/edit/106180525 was downvoted resulting in the deletion of the artist even though the there were relationships and pending edits:
https://musicbrainz.org/edit/106180528
https://musicbrainz.org/edit/106180527
https://musicbrainz.org/edit/106180526