Right.  Thinking a bit further, here's one way to avoid it:
The score/comment is only displayed to students in the module if send back via LTI 2.0.  (I.e. the existing LTI 1.1 grade endpoints won't set the Xmodule Fields). So the LTI modules already in use won't display these, but this is already the behavior anyway, so they'll be none-the-wiser.
I think this is a product call, so @Lyla-Fischer what's your opinion?