@bzbarsky has raised concerns a few times about the lack of formal definition of a task's document. The definition comes from the implied-document which is relatively handwavy.

Can we brainstorm some ideas how we can better formalize this?

For example I'm wondering if we can introduce a "queue a document task" and then we can change the call sites to "queue a document task given element's document". And then that could take the event loop from the document so we wouldn't need to use the definition of implied event loop either. Now that doesn't cover all the cases but would be a fair number of them.