Person A is one of the first to read a story, and has an interesting comment to make. This comment is immediately voted up, and there are several replies. Then Person B adds their interesting comment at root level. This comment goes to the bottom of the list, below all of the replies to Person A's comment. This leaves Person B's comment to be read only by those that make it all the way through.
The current system takes up a lot of vertical space for each reply, making it less likely that people will make it to the comments below. My idea is to put replies to comments directly to the right of the original comment, moving horizontally as more comments are added, so that each comment and its subtree takes up a much smaller amount of vertical space. This will allow those following a conversation to scroll from left to right, and those looking for different conversations to move from top to bottom.
Having a very wide site would probably cause no end of trouble, and I'm not saying that it's the optimum solution. I just think that it is an interesting idea to consider.
