new feature: collapsed comment thread expansion

[chasethestars]

copy/pasted from paidmembers:

Hi guys! We have a new experimental feature that is something a lot of people have been asking for: collapsed comment thread expansion!

This feature is in testing stages, which means that it's still in active development. It was created by our friends over at LJ in Moscow, and we'd love your feedback on it. Here's what you should know:

1. It's currently only available on entry pages using the Expressive, Expressive Winter, or Mixit S2 layouts. We do plan to expand it to other layouts (and the unstyled, site schemed entry page) once the kinks have been worked out. We also plan to make it available for use in custom layouts.
2. Paid users can use the feature on any journal using one of these layouts. Additionally, a user of any account level can use the feature on a Paid journal using one of these layouts. So it works if either the viewer or the journal being viewed is a Paid account.
3. To expand a thread, click the link labeled "Expand" next to comments in collapsed threads. This will expand that comment and all comments under it in the thread so that you can read these comments without going to a separate page.
4. There is a known issue that causes the "Expand" links to not work when viewing a journal with the ?style=mine argument (it will show the loading wheel forever and not expand anything). We hope to have this fixed by next week.

Again, we'd love your feedback on this feature. Let us know if you run into bugs and if you have any suggestions for how it should work. Thanks! :)