> I think that the principle of "code is data" is that data influences the algorithms either way, so there is not much of a point in separating the two.

This is clearly wrong in the sense that you allow your users to submit data to your website via a form, but you shouldn't trust that data in an `eval(...)` statement.

There is value in logically separating data / instructions. Having a physical separation may reduce some categories of bugs / security problems. Obviously as you rightly point out that the memory full of instructions has to get populated sometime, but when, how often, by whom, and with what safeguards are all relevant questions to the overall security of the model.

I think we generally agree, but you are taking the "code is just data" entirely too far to the point that you are blinding yourself to the value of the gradations in the middle.