From my personal experience (many many years of it) I find that there
are some people's code that is easy to read and understand and there
are other's that is not. One person's intent revealing code is not
always intent revealing to someone else.
It would seem ill-advised to try to understand a design in XP if you
cannot understand code.
If that is true, it would mean that anyone who is concerned with the
design has to be someone who understands code. Programmers understand
code. Who else really understands code?