I think it shows him as an articulate human who was rightly pissed off at them. PE were in the wrong and not afraid to show it.
(, Wed 27 Nov 2019, 22:05, Reply)
They are revelling in the embarrassment they caused him and the strop that he threw. They were chippy that he was going places (quite literally, the headed note paper is what really makes this letter) and he was abashed by his association with them. This was an aspiring proper writer, and a real doctor. The Eye back then was totally marginal, subversive and anti-establishment (none of those things are true today). The "mistake" was almost certainly deliberate, and got exactly the reaction they knew it would. Hence why the letter has been treasured for so long.
(, Wed 27 Nov 2019, 23:21, Reply)