I’ll say this: a lot of discussion seems to take place on Matrix chat that doesn’t make it into GitHub code comments as to why specific changes are made.

It used to be you could see the actual content of deleted comments and it was at the discretion of the client to show or not show them. The newcomers from Reddit (June) seemed to not like that people could read content of deleted comments, so I think changes were made for that reason.

With federation, it really isn’t reasonable to expect content copies to all be deleted. So it’s a complex issue.