...the propriety of Henry's remark. It is clear to Catherine that he is not proposing, but is he skirting the edge of propriety in using the word marriage with someone eligible like Catherine?

Certainly Henry is probing Catherine's sense of commitment to him. He may know she danced with Thorpe at the previous dance after refusing Henry (since Catherine later explained the situation to Eleanor) and has now allowed Thorpe to interrupt her preparations to dance with Henry by asserting that he (John) had a prior claim. Depending on how much Henry heard, he could wonder if Catherine was fickle. Certainly he seems satisfied with the conclusion of his probing.

“Mr. Thorpe is such a very particular friend of my brother’s, that if he talks to me, I must talk to him again; but there are hardly three young men in the room besides him that I have any acquaintance with.”

“And is that to be my only security? Alas, alas!”

“Nay, I am sure you cannot have a better; for if I do not know anybody, it is impossible for me to talk to them; and, besides, I do not want to talk to anybody.”

“Now you have given me a security worth having; and I shall proceed with courage. ... (Ch. 10)