1. The first thing that struck me was how very surprised Mrs Weston is that Mr Knightley does not like the friendship between Emma and Harriet ("You surprise me! (...) How very differently we feel! Not think they will do each other any good! This will certainly be the beginning of one of our quarrels about Emma, Mr Knightley.")

So, they have had these quarrels about Emma before it seems, so why is Mrs Weston so surprised at Mr Knightley's view? We don't know precisely what they have quarrelled about before regarding Emma, but Mrs Weston must be used to her and Mr Knightley thinking differently about her. Which is why her excessive surprise surprises me:)

2. Mrs Weston says she thinks Mr Knightley always thought her unfit to be Emma's governess to which he replies:
" Yes. You are better placed here - very fit for a wife, but not at all for a governess. But you were preparing yourself to be an excellent wife all the time you were at Hartfield. You might not give Emma such a complete education as your powers would seem to promise; but you were receiving a very good education from her, on the very material point of submitting your own will, and doing as you were bid (...)"

Is he serious or is this good-humored bantering between two good friends? It is not very gallant of him to tell her that she did a bad job with Emma, and that she shouldn't be a governess, but that she will make an excellent wife because she will submit her own will and do as she is bid. I hope this is good-humored bantering (he seems to be joking a bit in the next sentences), but is he a bit serious too?

3. "Emma shall be an angel, and I will keep my spleen to myself till Christmas brings John and Isabella. John loves Emma with a reasonable, and therefore not a blind affection (...)" Mr Knightley seems to set up his brother as an impartial judge on Emma. It will be interesting to find out what he has to say about Emma - whether he agrees with Mrs Weston, Mr Knightley or none of them.