@c1bc8fcb 
Here is the example from the screenshot:
https://social.heise.de/@heiseonline/111183389020062709 
And sorry, I don't have an Github-Account..

It is possible, that this behavior is not even new: Before the nice new preview-cards we would always post a preview-picture, suppressing a potential preview. Because I liked the preview, I asked my colleague to stop that and just post the link and let #Mastodon handle the rest.