In the past 30 days, I have produced 18 posts that have a total of 1621 comments. Removing my replies leaves approximately 800 comments - 45 per post.
Instead of using the number of 'active' users I am following, I will use the 11304 following me. 2812 of these followers have made at least 1 comment in the last 30 days.
And so you could state that 45 comments / 2812 active followers is around 1.6% of my active follower base making a comment on each post. As low as the number is, I suspect it is above average!
I used SteemSQL to construct my answer.