This is kinda crazy. You can't expect 100% of our comments to be brilliant. There needs to be some timeout or something, if not, people will start creating new accounts every day.
The number of people that can upvote is very high, yet most comments probably sit at 1 point despite not being mean or stupid. Now restrict that pool to 1000+ karma users, add a mental tax to the task, how many of those same comments are going to get two people to click "endorse" if they couldn't get one person to click "up"? I wouldn't put money on the rapid-fire sub-second moderation materializing, especially outside the top 10 stories or at odd hours.
I'm getting a stronger and stronger feeling that there is plenty of room for focusing the stated goal of this change, and then perhaps redesign the solution.
Please see references at my other comment:
(quoted to avoid readers having to click through):
[the following] seem relevant to this discussion:
Randy Farmer (I think this is what I remember) http://www.youtube.com/watch?v=Yn7e0J9m6rE
Bryce Glass (similar topic/similar takeaways)
What's wrong with the current system, by the way?
You can wish all you want, that people will use the endorse button in exactly this way and not the other.
Easier is, to simply wish that all comments will be thoughtful and constructive as they are posted.
You have about the same chance of seeing either fulfilled. Good luck!