What degree of borrowing from a Stack Exchange answer and submitting to a peer reviewed journal, without citation, is ethical? I posted a highly-upvoted answer on Skeptics Stack Exchange based upon numerous Chronicling America database newspaper quotations, and chatted in comments about this with a psychology professor.   

The professor, listing himself as sole author, then submitted an article with highly overlapping content to a peer reviewed journal, without any citation to my Stack Exchange answer. 

(More specifically, in Stack Exchange comments, I criticized a specific 2012 paper of the professor, which was primarily based upon google book ngrams, and showed in my answer numerous quotations from the Chronicling America database that result in a different conclusion. The professor then submitted an update of his 2012 paper to the same journal adding numerous quotations from the Chronicling America database.) 

Is this ethical? I've only published in chemistry/biochemistry journals and don't have any idea what is typical for psychology journals.
General Case

Ideally the author should acknowledge you in an acknowledgements section if you contribute assistance in some way. Unless you wrote part of the article, authorship is not warranted. 

This Case

The post your wrote was quite good and provides a lot of good material, but other than saving a researcher time, it doesn't appear to do any original research. That's in line with the policies of Skeptics.SE as well. Likewise, while the person asking the question has reasonable grounds to be skeptical of the claims, the thesis is not novel. 

I will also note that it the edit history shows that you started working on the answer in June 2017. The letter to the editor that you linked to says that it is in press as of the same month. I'm not sure what the lead time is like on that journal, but I wouldn't be surprised if the author has been working on the paper for significantly longer than you were working the Stack Exchange post. This is somewhat borne out by the author's publication history - they previously wrote on the same topic.

In short, it appears that you were both working on the same material independently before encountering each other.