According to Steemworld I've commented 3684 times in the 301 days since I created my account last July. This works out to 12 comments a day. I try and comment on interesting posts, people I know and anyone that creates interesting content.
I think this is vital for the growth of the platform and I also see people who post so much being more self-centered and not helping the community. COmments spark engagements and make the posts worth writing. What is the point of writing something if no one views it or interacts with it?