Earlier quoted context omitted.
The other thing is that his proposal was a proposal to "improve" Hacker News, not a promise to "fix" hacker news. Trying to do a grand massive "fix every problem" is more likely to introduce new problems than just making relatively safe improvements.
This is essentially the old argument over whether it's better to patch old bad code, or whether it's better to rewrite old bad code. I think all of the same responses would apply, i.e., whether or not new problems might be preferable to the existing ones. Since much smarter people than I have written carefully-considered essays on that argument (and without coming to a clear conclusion), I'll just let them speak for…
Let us not forget the object lesson from Digg's big redesign.