I wrote to hn@ and asked for this as a feature request:

"1. Delayed Karma Display. I understand why comment karma was hidden. I don't see the harm in un-hiding karma after some time. If not 24 hours, then 72-168 hours. This would help me read through threads with 1300 comments."

This was last January. While I asked for a few more features, it is the only one that seems essential as HN grows with massive threads.