This chapter establishes new characters and the suspense inherent to the convention of the marriage plot, which we have seen in all Austen novels thus far. Sidney Parker is introduced and appears to be a potential love interest for Charlotte, because she is our main female protagonist who has yet to meet a potential match (she clearly is not interested in Sir Edward or Arthur Parker.) Sidney is described as “seven or eight and twenty, very good looking with a decided air of ease and fashion and a lively countenance,” and is known to be single from the account of Mr. Parker. He is around the same age as Austen’s typical male love interests and although older than Charlotte, not by much. His introductions to her are described as “very well-bred” and “proper.” Although this information is largely the narrator’s perspective and Charlotte’s impression of him is not revealed, he seems like a contender in the potential marriage market Sanditon seems to suggest. Like other Austen love interests, he comes from outside of the original plot, later than other characters, similarly to Darcy’s introduction as a friend of Bingley’s in Pride and Prejudice. Also, he expresses opinions quite different from those of his family or the social circle to which he belongs. Earlier, Mr. Parker speaks of Sidney’s feelings towards his siblings and his propensity to ridicule their dramatic schemes and exaggerated illness. This and his relationship as brother to Mr. Parker, suggests a similar situation to the Knightley and Emma dynamic in Austen’s, Emma. However, Charlotte seems more like a Fanny Price character (Mansfield Park) than an Emma. Although she is more opinionated that Fanny, she is a quiet and observant character most of the time who has been minimally active in the plot thus far. Another reason to suppose their match is that Charlotte also rapidly recognizes the faults of the Parkers as hypochondriacs and sees through the schemes of Sir Edward Denham and Miss Denham. Her and Sidney seem at the very least, like they would be a compatible pair.

Furthermore, in the latter half of the chapter, Charlotte sees Clara Brereton and Sir Edward speaking intimately by the water, clearly intending their conversation to be private. Although Clara Brereton seemed to reject his affection in discomfort earlier, she speaks to him “composedly” and they seem engaged in “gentle conversation.” This contrast in Clara’s behavior is quite suspicious and seems to suggest an actual connection between the two, which could be a secret engagement similar to that of Jane Fairfax and Frank Churchill in Emma. However the rivalry the Denham’s have with Clara over Lady Denham’s inheritance could play into this attachment. This suggests a potentially duplicitous and coercive match similar to that of Mrs. Clay and Mr. Elliot in Persuasion.

Interesting that we have an Austen character, Arthur, so young, yet also so devastatingly and chronically ill, from Mary's account. Yet, this could be another exaggeration. Arthur's excessive concern with his health seems similar to that of Mr Woodhouse's characterization as a hypochondriac in Emma.

This article talks about the context of the seaside (and various seaside resorts) in Austen's writing:

https://www.regencyhistory.net/2012/09/jane-austen-and-seaside.html

The Romantic literary movement was obsessed with cottages: see William Wordsworth's poem "The Ruined Cottage" as an example.

http://www.jasna.org/persuasions/on-line/vol28no1/hall.htm

Austen emphasizes gender stereotypes in this section by highlighting the different expectations of the Parker's sons versus daughters and emphasizing Mrs Parker's submissive nature through her decision to give up the garden in their old house and submit to her husband's love of Sanditon.

Diana's seems to be a bit exaggerated in her account which reminds me of Mary's letters of her "illness" to Anne in Persuasion and hypochondriac Mr. Woodhouse in Emma.

"Beau Monde" is a French phrase meaning a world of high society and fashion.

https://www.merriam-webster.com/dictionary/beau%20monde

This sentiment seems to indicate a distrust of doctors as a whole. Is this a sentiment coming from Austen herself, knowing she was very ill at the time she wrote Sanditon? Or is it a tool she uses to present the Parkers as dramatic?

Vouchsafe means to grant a reply to someone.

https://www.merriam-webster.com/dictionary/vouchsafe

A billiard room is a recreation room for playing billiards, or pool rather.

https://www.merriam-webster.com/dictionary/billiard%20room