[tripzilch]

> How do you handle that anyway?

Reddit does it by limiting both the tree depth with a "continue this discussion" link (often seen in pun-offs) and the vertical tree length / number of replies with a "load more comments" link.

This ensures that the top thread is never really more than 1.5 screenlengths. Works very well IMO.

(For completeness sake, there's one other comment hiding feature, "Comment score below threshold", but that serves a different purpose--a bit like HN's [dead] comments except you can collapse/expand them and reply to them).