Hashtags / labels som that the content becomes curated.
Only sorting by upvotes / comments is too 1 dimensional for me, and it does not favours to the future readers of the site, nor to the goldmine content posted here.
Not a perfect solution, but the algolia search index is pretty good at finding topical articles that are most popular. If you don't use it already, it's the search bar at the very bottom of the front page.