Andree, not exactly, no; we do have that feature for sufficiently-long threads (10+ comments), but it turns itself on automatically. So, you'll see a "Read More" button after the 10th comment. 

I hesitate to collapse all by default, because there's often a ton of good stuff in the replies that I wouldn't want people to miss. That said, some kind of "collapse/expand all" control might be a handy feature.