How do you leave comments on someone's news feed on Facebook when he/she is not your friend?

[AuntieZoey]

One of my friends left a comment on someone else's page even though they are not friends each other on Facebook.
I wanted to leave a comment too, but a comment box never shows up.

[Nebi]

if the user does not allow comments, you can not leave comment on each page

[GirlyGirl]

that person who posted the post should have changed his privacy settings in a way that his friends of friends could comment on his posts. or may be your friend was tagged in that post. so that only the tagged people can comment on that.