I was wondering why dragging previews (to open a post in a new browser tap) didn't work while dragging others like tags did.
Then I tried inspector mode on Firefox and found these:
class="post-preview-link"draggable="false"
I reckon this is the setting of Danbooru because it's the same with Chrome, but I don't understand the reason for doing this other than causing unnecessary inconvenience, as people can still can still use their scrollwheel to do the same thing or right-click and open in new tap.