[dwild]

> If I make a post and then delete it, all comments (from everyone) should be deleted because the parent object is now gone.

Why does the ownership start at the post level and not the comment? If you consider that comments shouldn't be removable, that the post is now the owner of its child, what about the higher hierarchy. Is the forum category creator is the owner of the post too?

> However, it's insane that the rows themselves disappear, because there's no indicator that anyone else ever participated in that discussion (and thus most old comment threads appear schizophrenic)

If the cost of staying owner of what you post is a few comment threads that "appear schizophrenic", it doesn't seems like an high cost to pay.

[mudkip]

There are some valid points to keeping comments for posts that have since been deleted, and I don't necessarily disagree with them. For the sake of simplicity, however, I'm assuming that all of the comments on a typical Facebook post aren't going to be relevant if the post itself is deleted. On Hacker News, however, if the URL for this post stopped working, I think it's pretty clear that the discussion below continues to hold merit.

The ideal solution to comment threads would be to replace the usernames of people who simply delete their account with [deleted], but keep the content unless someone explicitly overwrites it. The biggest issue isn't that the content is gone (any given comment), but that nobody knows how many things are missing. It would be much better (with no loss in privacy) to at minimum just replace those comments with null text and a null owner, to at least show that 3 rows used to be here, between these existing rows.

[dwild]

> There are some valid points to keeping comments for posts that have since been deleted, and I don't necessarily disagree with them

Then your argument isn't about parent-child relationship, but value of the actual content. I can assure you, even if you don't give it value, there's one.

The funny thing, this is most probably why it's important to delete it if someone want to delete his content. It's his value, not yours, not Facebook's, no one else.

> It would be much better (with no loss in privacy) to at minimum just replace those comments with null text and a null owner, to at least show that 3 rows used to be here, between these existing rows.

I don't care about this.