> If we could edit our own posts, I could imagine that someone could modify what they wrote, to make someone who replied to them look stupid.
True, but there are reasonable mitigation strategies for that issue. Simply showing the time of the last edit solves most of the problem. For the rest, edits could be disallowed after replies are received (with a warning in the preview if a post was edited while you wrote your reply), or a different style could be used for posts which have been edited more recently than one or more of their replies. LWN could even record the history of each comment, which should be more than sufficient to keep everyone on their best behavior.