Collapsing a comment & chain is a huge missing feature for me. Also, one cannot get a permalink to a particular comment/reply nor a context link (ie the comment/reply a new comment/reply is responding to). Unless I'm missing that. I also wish the true/false difference in up/down votes were more distinct.
These are early days for a lot of these platforms, and really what's been built on kbin so far is impressive as it is. We're all used to feature sets that have existed for years so it's easy to think they are simple to implement, but that's not the case. I'm looking forward to seeing everything mature.
Edit: permalink is the timestamp/age next to your name at the top of the post.