I am not sure if this is right place to ask, but Why do I not see a comment button most of the times?
I have posted comments when I could, but when I needed to post one and do not see a way to do so [logged in, check] what do I do?
You need at least 50 reputation on each site to be able to comment everywhere.
You have 44 rep at the moment; one more (main site) upvote and you'll be there.