Cross out old comments when they have tasks or replies instead of deleting

[KurtWagner]

If a comment is no longer relevant it will be deleted. This used to cause dangling tasks and comments when such existed on the comment. Now it seems like the comment will just hang around, which gives the impression it's still relevant. I propose we either cross out (e.g, "Message: name is already declared") and/or label resolved comments as "Resolved" when we try to remove a comment that is no longer relevant