I've added a custom script that adds a hover effect for highlighting the vertical indentation bars of related comments, which I've talked about here (sort of; all previous levels are highlighted, not just the current one).
I think it could help editors to understand the new threading model.
If you want to try it, just add the following to your User:USERNAME/common.css page:
/* hover effect on thread bars */ .flow-replies:hover { border-left-color: #333 !important; border-left-width: 2 !important; border-left-style: solid; }