I try to comment on every stories I read, give my feedback and share my opinion, but even when sometimes I don't have anything to say aside from 'I liked it' I still comment that. Receiving karma points is just a bonus but the main reason is because I've written stories before and I know how much it can encourage authors and make them happy.

I really do want to comment on every story i have read but I'm not good with language and word so maybe that's why I keep silent

I do comment but not every time after I finished reading a chapter , when I have a opinion then ill comment...

I comment as much as I can... because I expect that from my readers as well

Yes I do. I mainly comment to thank the author for their hardwork and to share my opinion and etc.