1) Maybe the "cannot submit a comment if you have an pending comment" should be a per thread thing, rather than for the whole site.
I suspect a lot of people read in batches. They take a break and read a dozen new stories over the course of a few minutes. If the exclusion is site wide, and the endorsement rate does not turn out as high as you hope, that would in effect in many cases mean that they only get one comment per batch. If there are more than one story they want to comment in on a batch, they will need to remember to go back during another break and revisit the old story.
2) Won't someone think of the children? Suppose X comments, and his comment is endorsed, and goes live. Y sees it, and comments on X's comment. Y's comment gets endorsed and goes live.
If X and Y's aforementioned comments have each received an endorsement from a third party, count that as an endorsement of the conversation between X and Y, and allow their future comments to go live without endorsement if they are children of the X/Y conversation.
Take a look at the several long back and forth exchanges between tptacek and cperciva in this discussion: [1]. It would be a shame to impede such things.
It's only an issue if it takes a long time for comments to get endorsed, which we don't know yet. But if that is a problem it's easy to make the restriction per thread. I just wrote the simplest thing first.
You expect 1000ers to endorse most decent comments they come across that aren’t greyed out yet. Based on how many votes most comments currently have, I doubt that would be the case. Unvalidated comments would appear greyed-out, therefore suspicious, and most 1000ers would assume there is something wrong about them that they haven’t figure out. Especially if they expect to be punished for validated anything that isn’t exceptional… I’m not sure what ratio of comments you expect to weed out, but I expect most will be gone.
I suspect a lot of people read in batches. They take a break and read a dozen new stories over the course of a few minutes. If the exclusion is site wide, and the endorsement rate does not turn out as high as you hope, that would in effect in many cases mean that they only get one comment per batch. If there are more than one story they want to comment in on a batch, they will need to remember to go back during another break and revisit the old story.
2) Won't someone think of the children? Suppose X comments, and his comment is endorsed, and goes live. Y sees it, and comments on X's comment. Y's comment gets endorsed and goes live.
If X and Y's aforementioned comments have each received an endorsement from a third party, count that as an endorsement of the conversation between X and Y, and allow their future comments to go live without endorsement if they are children of the X/Y conversation.
Take a look at the several long back and forth exchanges between tptacek and cperciva in this discussion: [1]. It would be a shame to impede such things.
[1] https://news.ycombinator.com/item?id=7439363