It depends on what you mean by emphemeral because if you mean thr data's existence I would be against it. When I'm new to a domain or topic, I reference old threads all the time. I save links for other people and as reference points for me to dive into later.

Yeah a lot of stuff is what I wouldn't care about 2 minutes after I read it, but the protocol can't really know what any given person will want to come back to.