Boy, that is a good discussion question. One would like to be a "fly on the wall" to overhear what transpired between Anne and Frederick during their initial break-up. Like many of the details of Miss Austen's novels, she leaves this mostly up to our imaginations.

I find Capt Wentworth's cold civility towards Anne painful to read, don't you?

I personally think the captain's callous treatment is a bit of male bravado and that deep down beneath all of that he still burns a flame for Anne that, while just flickering, refuses to go out. After all, they have just been in each other's company only briefly after a very lengthy estrangement. Each is very cautious/guarded in this re-discovery period.