Give blog owners and people reading the comment section a way to easily toggle between viewing comments in the threaded configuration and the chronological view. There are major advantages and disadvantages to each, and being able to easily toggle provides the best of both worlds. You can see this sort of option on bulletin boards such as yahoogroups... no matter where a reader is in a comment series, they can easily see the option to toggle to the other viewing method - and even select a particular post of interest then toggle such that the new page display starts with the reader still focused on that comment. This is incredibly useful and helpful especially on high comment volume posts.
As it is, set to one or the other option exclusively, wordpress is not friendly to folks actively involved in blog comment sections. If on the threaded option it becomes far too time consuming to figure out just where the new posts are since you last read thru all of the comments. But if in chronological order only, there's no way to reasonably see if someone else has already replied to a specific comment making the particular point you have in mind - or to easily see replies to one of your own comments. An on-the-fly toggle view option is a great solution to these problems, and allows the user to work thru the comments in the most user friendly optimal way that I'm aware of. Bulletin Board and Blog Owners move to provider sites for just this option.
I know of at least two very high volume blogs that's been with you folks for a long time with owners who would very much like to have this option (along with an absolute boatload of their readers, who often ask about this issue), and in setting mine up, I sure would also like to be able to let readers easily toggle the comment pages between threaded and chronological views.
I'll even grovel: please please PLEASE create this option? Note also that the toggle has to reload the page in the new view pretty quickly, speed is important obviously. Regardless, I wouldn't think adding this functionality would be that difficult compared to the complexity you folks already manage to provide so well.