Personally, I prefer comments. I've never figured out how Medium calculates the time spent reading and the value of that time, but thoughtful comments from readers are always appreciated.

I try to respond to those, if a response is warranted. (If someone just says "Loved it!" I might just give them a clap or two in thanks - a hold-over from work emails where a "thank you...you're welcome..." string of emails is not really necessarily nor welcomed by most participants.)