I did not mean for my post to be read as advocacy for sex reassignment. My point was that much of the argumentation about sex reassignment is being mistakenly referred to science, which is not designed to answer moral questions.
There is not and may never be research on the therapeutic impact of sex reassignment — research that would compare to random-assignment, double-blind, treatment outcome research. For the time being, the best datum on the effectiveness of sex reassignment is that the great majority of properly screened, adult patients who undergo it say that they feel better.
It is indeed difficult to predict from a patient’s intake assessment whether that patient would benefit from sex reassignment. Fortunately, it is not crucial to do so. The old-fashioned “gatekeeping” requirement that patients live for an extended time in the cross-gender role prior to surgical eligibility screens out some or most patients who would not be happier in that role.
Leaving aside the moral, political, and cultural aspects to sex reassignment — the whole point of my original post! — I would say that patients should not be considered for hormonal or surgical interventions until they are age 21.