Is it a good counterexample? It seems to have approximately the same misuse resistance as parameter binding or equivalent apis. (For example, the dom api.)

In particular, this property of the described system makes it trivial for the unknowing or uncaring to subvert it: > It provides a string-management kernel that lets you create “safe strings” by certifying a regular string as representing either text or a fragment of a known language.

From what I understood, the certification is an unchecked assertion made by the program. One of the comments gives a great example of how this will go wrong in practice. The other aspect of this that is glossed over is that many data schemas represent all these things as "text". It is again an exercise for the program to get this right at the io boundaries.