You can already edit your comments? They give you a grace period of about 15 mins. Are you pissed when that window of time expires and you can't go and 'perfect' your posts?
The unofficial "List of Hacker News's Undocumented Features and Behaviors" maintained by minimaxir says that the grace period to edit is 2 hours and I think it's similar to what I remember from the last (recent) times I had to fix my comments. https://github.com/minimaxir/hacker-news-undocumented#editde...