This just in from Jessica on the Help Board [2]:

One of our CLs discovered the reason she couldn't see replies: her own screen settings. She zoomed out to 75% and all the replies appeared again! She reports: "I have always used Internet Explorer but I tried  Firefox, Chrome and IE and could not see anything beyond the initial thread post until I adjusted the zoom. I also just went back and clicked a Compatibility View under tools and it fixed my problem."

So try checking your monitor settings; maybe this will work for you, too! The team is still debugging the replies issue, but in the meantime let me know if this allows you to see replies.