Rich annotations on boards would be nice. More than what you can normally squeeze onto non-printing layers. I don't mean as a feature to add to the site, I mean the entire site IS partly this and I like the idea.

A way to discuss and explain things about a pcb that aren't easily written right on the pcb, like what happens in classrooms.

I often see myself drawing something a certain way on a board going up on github/pcbway/oshpark, and thinking someone else is going to "fix" this some day because it's not obvious why this bit here is drawn exactly this way, and I'm not cluttering up dwg.user with a paragraph of text for every other square cm...

And surely I am guilty of committing that same crime myself come to think of it.

This could help with that.