My experience is that it’s more like this:

• /c/one has 15 posts per day, 5 of them with 3 comments, the other 10 with none
• /c/two has 3 posts per day with 0 comments each

Not every post is a hit, so if you cast wide you’re likely to get a greater return on comments as something is bound to attract attention. The way the sorting works is that the 5 posts with 3 comments will show at the top and the 0 posts will drop off view, showing an active community.