I read the CLL 5:7 about {be} attachments. It wasn't mentioned there that we can pull {be} in front of the selbri. I am not an expert in formal grammars, but there we can find an answer to this point.
{pe} can also be nested. So why should {be} form an exception?
Jorge, what will you say?
It's not what he *will* say, it's about what he has said: I started to use nested {be}'s when
I saw it in his letters. :) As well as the rafsi {nun} for event abstractions, and modals used