@trwnh tbh I don't think there is a big difference between "quote" and "link preview" once it is posted.
The larger difference is that for creating a quote you usually just hit a button and type away, but for a link you need to find the url and copy paste it somewhere. If you'd like to do that often, quote functionality is way more convenient. Also quotes usually give the original poster a notification and links not.
@ConnyDuck so it’s primarily or entirely functional, with no semantic considerations?
i’m generally of the opinion that a “quote post” is just a button for inserting a link preview (could be opengraph!) that changes the thread (like setting a different context) and maybe sends a notification (like sending a Webmention)
so there might not be a reason to define rel=quote or similar property. but i am looking for contrary views.