This is a great observation. I had not connected Mrs. Smith’s speech about the sickroom to explain the engagement of Louisa and Captain Benwick. He with “an affectionate heart, needing to love somebody” and her with a “heart open, recently escaped from severe pain and recovering the blessing of health” make it seem inevitable that they fall in love over poetry as reasoned by Anne in Chapter 18. It is very sweet and I think his heart is worth having. Even Mary thinks so now that he is the means of blocking any more despicable Hayter connections.

Everybody's heart is open, you know, when they have recently escaped from severe pain, or are recovering the blessing of health." (Chapter 17)

“He had an affectionate heart. He must love somebody.” (Chapter 18)