Why does the narrative change back and forth between "Isabella" and "Mrs. John Knightley" to refer to Emma's sister?

Question

In chapter 11 of Jane Austen's Emma, I happened to notice that the narrative - not from anybody's specific point of view, but the narrator of the story - switched back and forth between referring to Emma's sister Isabella by her first name and by her husband's name. I've emphasized the relevant parts in this quote:

Mr. and Mrs. John Knightley, from having been longer than usual absent from Surry, were exciting of course rather more than the usual interest. Till this year, every long vacation since their marriage had been divided between Hartfield and Donwell Abbey; but all the holidays of this autumn had been given to sea-bathing for the children, and it was therefore many months since they had been seen in a regular way by their Surry connexions, or seen at all by Mr. Woodhouse, who could not be induced to get so far as London, even for poor Isabella's sake; and who consequently was now most nervously and apprehensively happy in forestalling this too short visit.
He thought much of the evils of the journey for her, and not a little of the fatigues of his own horses and coachman who were to bring some of the party the last half of the way; but his alarms were needless; the sixteen miles being happily accomplished, and Mr. and Mrs. John Knightley, their five children, and a competent number of nursery-maids, all reaching Hartfield in safety.

[...]; but the ways of Hartfield and the feelings of her father were so respected by Mrs. John Knightley, that in spite of maternal solicitude for the immediate enjoyment of her little ones, and for their having instantly all the liberty and attendance, all the eating and drinking, and sleeping and playing, which they could possibly wish for, without the smallest delay, the children were never allowed to be long a disturbance to him, either in themselves or in any restless attendance on them.
Mrs. John Knightley was a pretty, elegant little woman, of gentle, quiet manners, and a disposition remarkably amiable and affectionate; wrapt up in her family; a devoted wife, a doating mother, and so tenderly attached to her father and sister that, but for these higher ties, a warmer love might have seemed impossible.
[...] He was not a great favourite with his fair sister-in-law. Nothing wrong in him escaped her. She was quick in feeling the little injuries to Isabella, which Isabella never felt herself. Perhaps she might have passed over more had his manners been flattering to Isabella's sister, but they were only those of a calmly kind brother and friend, without praise and without blindness; but hardly any degree of personal compliment could have made her regardless of that greatest fault of all in her eyes which he sometimes fell into, the want of respectful forbearance towards her father.
_{Emma, chapter XI (emphasis added)}

I also noted that, a bit later on, the text switches back and forth between "Mr. John Knightley" and just "John Knightley", but that's not the focus here.

What's the significance of switching bacck and forth here? Are there different connotations of using her first name and her married name in different contexts? What's the reasoning behind using one in one place and the other in another, including switching within the same paragraph?

Answer 1

As noted in this earlier answer, to a different question about part of this same passage, Austen was pioneering the free indirect technique in Emma. The switch back-and-forth between "Mrs John Knightley", "poor Isabella", and "Isabella" indicates which point of view is being portrayed:

• "Mrs John Knightley" is a neutral third person way of referring to the character.
• "Poor Isabella" is how Mr Woodhouse, the father of Isabella and Emma, thinks of her. Mr Woodhouse is convinced that Isabella must suffer greatly, having to live in London with her own family instead of remaining at Hartfield with himself and Emma. The soubriquet is characteristic of him. In the very first chapter of the novel, when George Knightley returns from a visit to London and visits Hartfield to give Emma and her father news of John and Isabella, Mr Woodhouse makes "many inquiries after 'poor Isabella'". So when the narrator here says that he would be unwilling to go to London even to see Isabella, she is naturally "poor Isabella" again.
• "Isabella" is how Emma thinks of her sister. When she thinks of John Knightley's attitude toward her sister and herself, the narrative voice switches to her point of view (by far the most prevalent in the novel; the others are mere asides), and so the character is now "Isabella" tout court rather than "Mrs John Knightley" or "poor Isabella".

It bears mention that Isabella is referred to as Mrs John Knightley for two reasons.

• First, to disambiguate. Were she referred to simply as Mrs Knightley, there might be some confusion, as that form of address would apply equally to any hypothetical wife of George Knightley's.
• Second, because John Knightley is the younger brother. Since the Knightley brothers' father is no more, the elder, George, is Mr Knightley. The younger is Mr John Knightley. This convention is common in that period; for example, in Pride and Prejudice, Jane is "Miss Bennet" while her sisters, the other Misses Bennet, are "Miss Elizabeth Bennet", "Miss Mary Bennet", etc.