https://opensea.io/assets/ethereum/0xd5e793C08ce6e4bc225b64F19496629A81873C22/646

This is embedding a Wapuu NFT via the NFT block.

https://quixotic.io/collection/0x62007C1e6b17b9f28434B3B24e9654aA12439eCb

This is embedding a Mirror article via presumably oEmbed.

https://opensea.io/assets/0x62007C1e6b17b9f28434B3B24e9654aA12439eCb/101

And this is embedding the same article via the NFT block.

And it is editable.