You're right but looking at raw the image is actually flagged as a thumbnail. Thunder, Jerboa and browser ui open the link when tapping on it.
I believe Summit incorrectly flag posts as text when there is a link followed by a thumbnail. Thunder and webui flag this kind of posts as a link.
Summit probably already does something special as it shows the thumbnail first : raw shows the link is before thumbnail. But imho, it should combine the link and it's thumbnail.
As I keep tapping on the thumbnail which is never what I want to see, is it possible if no official info exists on how to handle such cases to at least add an : "open links for links followed by a thumbnail if tapped" or "Show links followed by a thumbnail as an image link" ?
Hope I am not coming as negative. No matter what Summit is a great app and I am grateful for the enormous time you're probably spending on it.