ranking is based on favorites/comments rather than a hidden algorithm
But there has to be an algorithm to decide how to rank based on favourites and comments, and I couldn't see that algorithm described anywhere on the site, so I dare say that it's hidden.
Small gripe with the site, it somehow has the "swipe with two fingers sideways to go backward or forward in the browsing history" gesture disabled, which is kinda annoying. (macOS with Firefox)