I think the main reason is to keep the context of a discussion in a thread.
Turning your question around: Why would you want to modify a comment after one hour?
Read your comment before posting and be happy with it at that time of posting. If you come to new insights later then post another comment. There's no shame in that.
I might want to modify it after one hour for the same reason I might want to modify it after one minute.
Perhaps I'm not checking HN regularly that day and make an offhand comment. In that case, if I come back a few hours later and recognize a boo-boo, it would be nice to be able to correct my mistake to avoid a permanent record of my foolishness.
Another way to avoid a record of foolishness is to think before posting foolish comments. I think the defaults here are set to provide an incentive for that behavior.
I think your last sentence "and recognize a boo-boo, it would be nice to be able to correct my mistake to avoid a permanent record of my foolishness"
How can you make a mistake in a comment? If you don't mean what you write don't post it... And don't worry about people calling you foolish (I am sure there is a famous quote for that to put it more eloquently).
Also, note that there is no post preview when you submit so being able to modify after you post fills that functionality gap.
Sometimes I come back later to find that people have misinterpreted my comment due to tone or incomplete or misstated argument. Within the hour I can add an "EDIT" to clarify what I meant. I suppose I should take the time to make is sound in the first place, but often the time isnt there.
Perhaps a reasonable compromise would be to have the ability to add a timestamped addendum, without being able to edit the original. I would still want the one-hour free edit though.
You need to be able to modify comments for some amount of time to correct typos, but if you can modify them for too long you can rewrite history. The current time limits are arbitrary but seem roughly correct, judging from the fact that users complain roughly equally about missing typos till it's too late, and people they're arguing with rewriting their comments.
It seems the assumption is that after you make a comment you are actively checking the thread for some time afterwards. Perhaps this works here because of a correct assumption about how people use HN but a time-constrained lifestyle might prevent this in some other groups.
What about letting people append to comments after the time limit? I've always thought that would be sensible: People could add to what they've said before in a visible way, but not "rewrite history".
After all, additions are already frequently marked as such (e.g., "EDIT:").
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[ 3.3 ms ] story [ 36.8 ms ] threadTurning your question around: Why would you want to modify a comment after one hour?
Read your comment before posting and be happy with it at that time of posting. If you come to new insights later then post another comment. There's no shame in that.
Perhaps I'm not checking HN regularly that day and make an offhand comment. In that case, if I come back a few hours later and recognize a boo-boo, it would be nice to be able to correct my mistake to avoid a permanent record of my foolishness.
How can you make a mistake in a comment? If you don't mean what you write don't post it... And don't worry about people calling you foolish (I am sure there is a famous quote for that to put it more eloquently).
Also, note that there is no post preview when you submit so being able to modify after you post fills that functionality gap.
Perhaps a reasonable compromise would be to have the ability to add a timestamped addendum, without being able to edit the original. I would still want the one-hour free edit though.
As it is there is already plenty of that going on.
I'd be fine with locking a posting or only amending it after it gets 1 comment or upvote (or downvote).
After all, additions are already frequently marked as such (e.g., "EDIT:").