MicrosoftOur tedious workaround is to tell everyone who cares about a Task/Card (creator, assignee(s), watchers) to comment something random in it (like a dot "." or "WIP" or "watching" ) the first time they see it.
This makes things look a bit ridiculous & creates some Spam when the task is created, but ensures that the one who just commented will get notified of all future posted comments via email as well (NB: not all future Changes, like to the Title, Description, Checklist, Attachments -- just future Comments).
This is because the Comment thread of any Planner Task is an *actual* rendering of a O365 Group Email thread for that Task & every new person to comment gets added to the Senders list from that point on.
I.e. the Comment function has been a quick hack all these years & it continues to be ignored.
