As I said in two separate lectures yesterday:
How many comments do YOU make daily?
The internet is entirely give-to-get. To get something out of it, you've got to put something into it, and that includes comments.
There will ALWAYS be more spam than legit comments. Especially since the ubiquity of Facebook and Twitter, the "commenter urge:" has been bled off to other platforms, so suddenly every commment you make is rare and important. I used to routinely get 40 comments per post in the first day. Now I frequently get none, but I do get lots of rt's and some comments on Facebook.
I calculate comments come at a rate of about one per seven hundred readers now.