that in retrospect, Elinor could look back on Edward's behavior towards her, and always find it to be proper and friendly, but never "engaging", as we see Willoughby with Marianne. Edward never really seems to single Elinor out, and is actually more animated talking about twisting trees and leafy walks with Marianne than he ever is with Elinor. And then there's this from the book:

"Without shutting herself up from her family, or leaving the house in determined solitude to avoid them, or lying awake the whole night to indulge meditation, Elinor found every day afforded her leisure enough to think of Edward, and of Edward's behaviour, in every possible variety which the different state of her spirits at different times could produce; -- with tenderness, pity, approbation, censure, and doubt."

Elinor doubts Edward's regard for her. There has never been any doubt about Willoughby's regard for Marianne, and while Elinor might be teased about Edward, Marianne is thought to be outright engaged from Willoughby's treatment of her.

I don't see Edward as sporting with anyone's affections. He lets Lucy know that he's tired of her in word and deed, and Elinor knows that he regards her as a friend, but has never been led to believe beyond that, no matter how much she hopes.