One of the key aspects to realise about Jane Austen as a writer is that she is a narrator who insists on being there right along with the action, and putting a good or a bad word in for a number of her characters. This is an important aspect of her style as an author, and one that we must be aware of. Other authors, for example Hemmingway, is famous for remaining incredibly detached during their narration. They remain distant from their characters and the action, and don't offer their own responses or thoughts about characters or what is happening. The first quote you have cited is an excellent example of Austen's role as an intrusive narrator, which of course shows how opposite to a detached narrator that Austen is. She is definitely not afraid to tell us what she thinks we should think about characters and situations, making her sympathy for Anne clear from this initial quote.
The second quote is an example of how Austen wins a level of trust and veracity for Anne, which means that in the novel we accept the veracity of her impressions and ideas of others, such as Captain Wentworth. Having been identified as such an excellent character, we can only suspect her of being innaccurate if we are willing to distrust the narrator.