When using a Publish Service such as 500px or Facebook, don't forget you can check for comments and other things like ratings and likes.
Comments is the last panel in the Right Panel of Library.
To refresh see new comment, click the refresh icon on the left of the panel header.
Here I'm refreshing my comments from a post to my Public Profile on 500px.com
And there's the comments and the pictures rating on 500px, without needing to go to the site. The photo is of Blackrock Diving Board in Salthill if you want to see it bigger!
Facebook will show Likes as well as comments.