Please explain what Emma means by saying the following to Mr. Knightly in Vol 2 Chapter 8 of Emma by Jane Austen.
"Yes I should, I am sure I should. There is always a look of consciousness or bustle when people come in a way which they know to be beneath them. You think you carry it off very well, I dare say, but with you it is a sort of bravado, an air of affected unconcern; I always observe it whenever I meet you under those circumstances. Now you have nothing to try for. You are not afraid of being supposed ashamed. You are not striving to look taller than any body else. Now I shall really be very happy to walk into the same room with you."
The explanation of Emma's remarks lies in Knightley's circumstances and inner character as well as in the immediate situation. Happily, Austen summarizes Emma's view of Knightley's circumstances and inner being two paragraphs ahead of your quotation. She also privileges us to an account of Emma's opinion on Knightley's circumstance and inner traits.
Knightley, the Austen-narrator tells us, has more health and independence than he has spare wealth (this is not to say he is in any way in tight financial straits like Mr. Bennet of Pride and Prejudice), thus he prefers the exercise of walking to the expense of keeping a carriage horse solely to pull his carriage. Emma disapproves of this physical sacrifice of the dignity of his position as the chief gentleman of the district and the lord of Donwell Abbey. Emma prefers to see him arrive at places in state, looking well kempt, not disheveled by exercise, and seeming the gentleman that he is.
Mr. Knightley keeping no horses, having little spare money and a great deal of health, activity, and independence, was too apt, in Emma's opinion, to get about as he could, and not use his carriage so often as became the owner of Donwell Abbey.
The immediate situation is that Knightley has arrived at the ball in his carriage just ahead of Emma having arrived in her father's carriage. Emma is delighted to see Knightley deport himself in this luxuriant style as befits a gentleman, and she tells him so. With ironic laughter, Knightley says that he is sure that Emma would not have been able to tell that he looked more the gentleman had she seen him for the first time inside the ballroom, not having seen him arrive in his carriage. His ironic meaning is that, of course, Emma's ill-founded premise that he looks more the gentleman when he arrives in proper state has no relationship to fact. "I doubt whether you would have discerned me to be more of a gentleman than usual."
Emma's reply constitutes the quotation you ask about: "Yes I should, I am sure I should." In other words, Emma takes up the debate with Knightly and insists that she would be able to see that he had come in a carriage because the "consciousness or bustle" that plagues people who arrive in society in an unorthodox manner, by walking for example, would have been absent and his deportment more natural: he would not be "afraid of being supposed ashamed ..." and would not thus be "striving to look taller than any body else." The conclusion of this important analysis of Knightley's inner qualities by Emma is that she now "shall really be very happy to walk into the same room" with Knightley.
"This is coming as you should do," said she; "like a gentleman.—I am quite glad to see you."