Encrypting parts of a Text-Node

Dear XML Encryptors,

I asked at the workshop, but I didn't get the solution:

How do we handle the following: A text node is split into two (or more) 
text nodes and some of them are beeing encrypted. I agree that this SHOULD 
NOT be allowed, because if we don't mark up the to-be-encrypted text - 
include the text in a dedicated element - the text is not important enough 
to be encrypted separately.

But IF we do so - we cannot see this from the resulting ciphertext. Shall 
something like that be mentioned in a spec?

Christian