I also can't seem to figure out how to consistently jump to the next top level parent comment with the nav button. It seems to jump to other comments lower in the current thread which I'm trying to skip past. Am I missing something?
Overall love the app though. Love that I can click a user name and see their profile.
One other odd thing is when I open a HN Notify email link telling me I have a response, I can't figure out how to go up a level from the response comment to my parent comment they responded to in order to remind myself what I posted.