Deactivated user doesn’t show up (under subject) in logs if they are deleted. This is because we store target user ID in logs, and if that user gets deleted there is no associated account with that ID.
I added the location as context to deactivated user logs which contains user ID and username via:
https://github.com/discourse/discourse/commit/3a6e137e70c0d57e977679b8a39494c17b1c469e
This is how the “deactivate user” log will look now:
Note that this change will apply on all future deactivations.