When suggesting a major change like this, I think that it'd be a very good idea to do some back of the envelope calculations using data that you could probably get straight from the DB.
My starting assumption would be that all users with 1000 karma actually keep reading all comments as they can do now. Some might visit a 'new comments' page to make sure posts by new posters get promoted. Others will just filter them out completely. So we might as well start by claiming both effects will counteract each other.
So take, say, the last week of submissions, and see how many comments that actually received an endorsement are made by noobs like me that have less than 1000 karma. Then, take a look at how many of those comments were endorsed by members that have more than 1000 karma, then, check how many were endorsed FIRST by someone that had 1000 karma.
Given the starting assumptions, this would give you a pretty good idea of how many comments would just stop receiving karma altogether, how many would receive less, because people would not be able to see them before a 1000+ user promotes it, and how many would remain roughly the same.
Then, you can add your own bias on whether you think people will be more active at promoting those new posts, or if they will be more easily forgotten. But without some hard data, all you are doing is making a major change to the site, with no idea of what it's really going to do.
I am sure this information would also be considered useful by anyone geeky enough to visit Hacker News, and you could use it to defend your position, one way or the other. It's harder to be outraged when a proposal like this comes attached to some nice evidence.