If it takes longer to read, it's not an AI problem, but the author failing to catch that the comment is too drawn out. I don't see how it is a problem to have AI write a comment if you agree with the content. If it is bad content, it will eventually reflect badly on the author anyway.
I skim 100 comments here everyday. Good comments/bad comments, overly long comments, whatever, time to read is low. I assume all those authors have a strong opinion / expertise on the subject that urged them to take the time to write that comment, which makes skimming hacker news to keep a pulse on the world (imho) a valuable task. If, instead, most of those comments are composed by molt-bots, then I'm not getting a "real" view of the world, I don't care how good and concise the comments are, I'd be wasting my time reading about news that may not matter to anyone and opinions that may not exist.
