We are the writers and readers that form the community, and we expend energy here. Comments are interactive if the author responds, and are a way of supporting a conversation, which in turn builds a sense of community.
Medium launched 7 years ago. Illumination is young and thriving thanks to you, Dr. Y! The way to know we matter comes from interactions - the metrics of claps, curation, and reading time can indicate some feedback for the writers, but for me, I agree with you - comments matter most.