The community member's post describes an issue where external links from content embedded from Ghost are getting a ?ref={Ghost URL} parameter added, which is causing issues with at least one of their sites. In the comments, another community member provides the solution, stating that the issue is due to a setting in Ghost's Analytics called Outbound link tagging, which needs to be turned off to stop the ?ref= parameter from being added to external links.
Just for future reference as this is likely to come up for someone else, I was able to track the behaviour back to Ghost. There is a setting under Analytics called Outbound link tagging that needs to be turned off to stop the ?ref= from being added to external links.