I like that Austen shows Elinor and Colonel Brandon to be good friends with no romantic interest in each other.
I think it’s harder to see because the falling in love happens off-page but I get the impression in chapters 17 & 18 that Elinor and Edward share a similar sense of humor. Like when he says that if Marianne were wealthy she would by every copy of Thomson, Cowper and Scott, “to prevent their falling into unworthy hands” His comments about the picturesque (“I shall offend you by my ignorance and want of taste, if we come to particulars. I shall call hills steep, which ought to be bold! surfaces strange and uncouth, which ought to be irregular and rugged;… I do not like crooked, twisted, blasted trees. I admire them much more if they are tall, straight and flourishing. I do not like ruined, tattered cottages. I am not fond of nettles, or thistles, or heath blossoms. I have more pleasure in a snug farm-house than a watch-tower ....”) remind me a little of Elinor telling Marianne that not everyone share her fascination for dead leaves and Elinor laughs in response to Edward’s speech I don’t remember Colonel Brandon ever making her laugh.
Edward makes a number of mistakes but I can sympathize with how he got himself into such a mess. I can see how he convinces himself he’s not engaging Elinor’s affections.