What are the green checkmarks on the profile page

On my profile page there are green checkmarks next to some posts but not all of them.

When I hover over a green checkmark there is no flyout indicator telling what it is.

I can see that some checkmarked posts are responded to by me and some are responded to by other people. So that's not it.

Does it mean that the post is Active? Closed? Done? Good? Points awarded?

Thank you,

Chris