This would really be a nice feature update. I know that when they designed it, the 6 level nesting was there because the author would get a split of all the comment payouts (up to 6 levels deep), as a reward for creating a post that encouraged a lively discussion.

I have no idea if this is true or not, but I've heard rumors that they removed that. Someone should be able to find out fairly easily.

If they did, then there is not really a reason to keep the 6 level nesting restriction anymore. If they are still doing the author payout for 6 levels of comments, then they probably could not do this without a hardfork.

Either way, I think it is a good idea - just different levels of difficulty to implement :)

I included a link to your post in my list of proposals to enhance the Steemit website:
https://steemit.com/ui/@timcliff/let-s-make-steemit-better-comprehensive-list-of-suggested-ui-ux-improvements-to-make-to-the-steemit-com-website