The equation of the white jacket with Dr Monygham's "concession" suggests
a white flag of surrender, of the sort he exhorts to be raised in Chapter 3-10.
I.e., Dr Monygham, who distrusts people's motives, has surrendered in this case
to an example of "character" worthy of "respect." "Character"
is a key recurring word in the novel, signifying the valuable inner soul that
is the only redeeming aspect of the otherwise tragic human condition.