If I'm interpreting MBS-8287 correctly subscribers are supposed to be notified via the regular "Edits for your subscriptions" email once an artist (or other entity) from a subscribed collection is deleted or merged.

I have an artist collection with plenty entries that get regularly deleted by modbot and subsequently removed from the collection but were never notified when it happened.

E.g. https://musicbrainz.org/edit/81889642 was deleted on 2021-08-14 but neither for that day nor the following did the subscription notification email inform me of this event.

I know for a fact that this artist was part of said collection thanks to my browser history.
Added on 2021-08-12:

https://beta.musicbrainz.org/collection/<MBID>/collection_collaborator/add?artist=2204764&returnto=%2Fartist%2Fd24dd4f0-49f6-4115-a73a-f814e273dfdd