You let the comments themselves have upvotes. Look at any of the technical subreddits - typically domain experts end up being near the top comments naturally,

You let the comments themselves have upvotes. Look at any of the technical subreddits - typically domain experts end up being near the top comments naturally, because they lay out substantive comments. Reddit "flair" is a solution as well. Ideally a platform like this would be able to connect to a LinkedIn profile, and display some relevant info from said profile.