Thanks for the suggestion, David! I will add this to the list for our team to review :) Have a great day!
UPDATE:
At this time, the team doesn't feel that it will be able to add specific sorting support (like the requested Hacker News / YCombinator). However, if you still want to use FlowReader and receive their news - here's their feed: https://news.ycombinator.com/rss :D Sorry for any inconvenience!