For me it is only triggered when I search for a forum post and click from there. For example:
I clicked this article from the front page:
Here is the link from the front page, no search:
Sorry for the large links, I thought there was a way to shorten them but I must have forgotten. I hope that helps!
After testing the same idea of it being linked to the search I tried every article on the front page with the same results. I even tried it with this post and I can indeed confirm for me the insertion only occurs when using the search.