According to the Stanford University libraries,
What Is Fair Use?
In its most general sense, a fair use is any copying of copyrighted material done for a limited and “transformative” purpose, such as to comment upon, criticize, or parody a copyrighted work. Such uses can be done without permission from the copyright owner. In other words, fair use is a defense against a claim of copyright infringement. If your use qualifies as a fair use, then it would not be considered an illegal infringement.
So what is a “transformative” use? If this definition seems ambiguous or vague, be aware that millions of dollars in legal fees have been spent attempting to define what qualifies as a fair use. There are no hard-and-fast rules, only general rules and varied court decisions, because the judges and lawmakers who created the fair use exception did not want to limit its definition. Like free speech, they wanted it to have an expansive meaning that could be open to interpretation.
Therefore, according to my interpretation, using that image was indeed a copyright breach, regardless of it being referenced and linked to. Indeed, I was neither commenting, nor criticising, nor making a parody of the copied content. I was using that image without permission to enhance the content of my answer. Hence why I edited it out of the question. In addition, I have re-visited my interpretation of Fair Use.
Personally I would have been fine with someone else editing the copyrighted picture out of the post. I am in favour of free edits aimed at improving the quality of a post.