@Edent
The spec doesn't address this but does have an example where the <blockquote> is in a <figure> and the metadata is in <figcaption> (I don't think <figure> would be best as the outermost element for embedded social media posts).
In the post footer, I don't think the likes, replies, reposts should be inside link, only the timestamp.
https://html.spec.whatwg.org/multipage/grouping-content.html#the-blockquote-element