] However, Willoughby says himself that when he first started trying to attract Marianne, he didn't know what love was. Falling truly in love (at least as much as he was capable of) took him by surprise, and deepened his understanding of what it was like to suffer for love

Ah! But he did not love Marianne. He not only says that he didn't know what love was when he started playing games with Marianne's affections, but he also asks:

"But have I ever known it? -- Well may it be doubted; for, had I really loved, could I have sacrificed my feelings to vanity, to avarice? -- or, what is more, could I have sacrificed hers? -- But I have done it."

He realizes that not only did he not know what love was when he met her, but that he could never have subsequently treated her the way he did treat her if he ever *did* love her.

The one thing I will say for him is that at least now he realizes that a man who is really in love with someone else would not be capable of the kind of treatment he gave Marianne. Interestingly, this admission of Willoughby's echoes what Colonel Brandon said about him back in Ch. 31: "...he had already done that, which no man who can feel for another would do. "

If a man loves someone, he doesn't go around abandoning her for someone with better financial prospects, humiliating her in public, avoiding her, lying to her etc. He doesn't wish that she will never be happy with anyone else if he can't have her.

A careful read through his message reveals that he never does say he loves/loved Marianne. The best he can manage is that he became 'sincerly fond' of her, even when Elinor asks him point blank whether he was ever really attached to her. It's actually quite brilliant the way JA wrote it, because it gives the impression that it is 'implied although never professedly declared' to paraphrase Marianne. But, the bottom line is that it is NOT declared--he never said the 'L' word to Marianne herself, and he doesn't say he loved her here either.