I have seen JA's use of the word "reserved" as a personality trait before, most notably in Emma's Jane Fairfax. However, it was not until this GR that I paid any particular attention to the conversation at the end of Ch. 17, which includes the following exchange:

"She knows her own worth too well for false shame," replied Edward. "Shyness is only the effect of a sense of inferiority in some way or other. If I could persuade myself that my manners were perfectly easy and graceful, I should not be shy."

"But you would still be reserved," said Marianne, "and that is worse."

I think that in my mind, I have always thought of shyness and reserve as being nearly synonymous. Upon serious reflection on this passage, though, now it seems to me that shyness is, as we use it now, a state of self-consciousness or fear of people thinking ill of us. Reserve, on the other hand, is... what? Deliberately withholding conversation or information? Quietness that springs from some other source than self-consciousness? What does JA mean by it? Marianne feels that reserve is worse than shyness - is it a character flaw rather than a personality trait? Edward is very upset by the implication that he is reserved, is it something he ought to be ashamed of?