merely facing up to Minerva McGonagall is enough to make him have to excuse himself and go retch

This line has actually been changed to:

he grabbed the magical self-cleaning towel and, with shaky hands, wiped moisture off his forehead. Harry's entire body was sheathed in sweat which had soaked clear through his Muggle clothing, though at least it didn't show through the robes.

(at the end of ch6)

It doesn't take away from your point, just remarking that there are some details in the early chapters that have been changed.