Just like most things on HN, once you have submitted it (either comment or article) it becomes the record. You have a limited time to edit things, but after some time you could go back and "rewrite" the conversation, this type of thing prevents that.

Deleting content disrupts conversation, see eg [deleted] on Reddit where people can delete their posts anytime.

yeah, but if you could delete a post that received 0 upvotes [i.e. nobody values it] and not a single comment then deleting it wouldn't annoy anybody.

Some people game the system.

Allowing people to delete and resubmit articles is another opportunity for people to game the system.

I used to do that before, not knowing that it's against the rules. I don't do that anymore.

Thank you!

Think of it like sending an email. You can't edit it once you send it.