A facility for quotation covers the absence of original thought.
Perhaps one should take this admonishment as a warning not to set too much store by a quote; after all, Wimsey is right, in many ways. By continually quoting from the brilliance of others, one is able to sound insightful and erudite whilst simulatenously being neither. The frequent use of quotations does need some level of understanding, to make sure that it is relevant to the situation into which it is being interjected, but it also requires no original thought whatsoever, and so requires only that the "quotationer" has a good memory, rather than a quick wit.
Lord Peter Wimsey sets great store by wit, and sharpness of mind, and so is rather scathing about anyone who over-uses quotations without ever coming up with an original thought or observation of their own.
In the glamour of one Gaudy night, one could realize that one was a citizen of no mean city. It might be an old and an old-fashioned city, with inconvenient buildings and narrow streets where the passersby squabbed foolishly about the right of way; but her foundations were set upon the holy hills and her spires touched Heaven.
Oxford is an old city, steeped in tradition. and Harriet references the poet Matthew Arnold when she mentions it spires; Arnold wrote of Oxford's "dreaming spires" in his poem Thyrsis. Oxford is also a town that seems vaguely mysterious because of the gothic nature of the buildings. Harriet is apprehensive about attending the Gaudy Night dinner, because she does not know what kind of reception she is going to get, but the city draws her in again, and reminds her of what it was that she loved about her days as an undergraduate. She also realizes that the very appearance of Oxford enables her to hide in academia, in its own little world, rather than facing what is going on in the real world outside the safety of college.
I know what you're thinking - that anybody with proper sensitive feeling would rather scrub floors for a living. But I should scrub floors very badly, and I write detective stories rather well. I don't see why proper feeling should prevent me from doing my proper job.
It would be wonderful to say that things have changed a great deal since Sayers wrote the Harriet Vane novels; sadly, cleaning supplies manufacturers still market their products almost exclusively to women, as though mopping floors is their true calling in life. Harriet is feeling a degree of criticism for her life choices and for the fact that she wants the freedom to choose her own destiny instead of having society choose if for her.
This is also especially relevant in this novel because the writer of the poison pen letters, Annie Wilson, deeply resents and dislikes women who work in academia rather than in domestic service, where she feels they belong. This is something that society has been brainwashing women like Annie to believe and unfortunately, because she is envious of women like Harriet who is able to pursue her own dreams, she feels the need to persecute them.
