It would probably be more respectful not to copy what they posted along with their username. Actually, I think we'd better redact the username from your quote. People sometimes have important personal reasons for deleting things. The odds aren't high that it matters but the impact could be high if it did.
People sometimes have important personal reasons for deleting things but this does not mean anything. It is not as if "x posted y on twitter and deleted it afterwards" or "the page was edited/deleted, here is an archive.org link" is uncommon on HN, nor it is as if a stalker would not be able to scrap HN posts of someone instantly as they were posted.
> it disappears.
In my experience they show as [deleted] but I guess this is only for posts that have replies.
Kind of. Technically, posts that have replies can't be deleted, so what sometimes happens is the poster edits their post and replaces all the text with "[deleted]".
Which should also be prohibited, because it's just as destructive. You shouldn't be able to edit a post with replies either.
Yes, ideally I would just do more revising before posting a comment the first time, but I don't seem to work that way.
I think the two-hour window is a good compromise, and if anything I really wish it was longer. Yes it has downsides, but I really think they're outweighed by the good.
I'm sure it wasn't that big a deal and I'm sure your intentions were good, but I'm also pretty sure most HN users would want us to protect them in this way, if only for the rare occasion on which it actually is a big deal.