– has anyone encountered that blackness before?
An issue with Twitter, I assume.
If it helps to understand possible causes of the misreprentation above, here’s a screenshot of an earlier view of the same tweet (probably taken soon after it was posted):
In that early shot, Twitter’s representation was of the first of the three links. There’s the
/about text for the forum.
In all later views of the same tweet, in a variety of browsers (including non-extended Firefox 53.0), Twitter’s representation is of the third of the links.
You are referring to oneboxing, which is the opengraph or oembed tags for a page. View source to see what image was selected in those tags, on the target page.
Use iframely.com/debug to troubleshoot.
Generally if you don’t like the image being chosen for oneboxing, remove it from the page by pressing the edit button.