I agree Mr. B and Lizzie are more alike than not but Lizzie doesn't avoid situations as Mr. B does. Their character and humor are similar but unlike Mr. B, Lizzie would never hide in her study to avoid an uncomfortable situation around her. I think the subtle diffrences are also admirable to Darcy, which also will make their marriage a happy one, in my opinion of course. Though their is hardly an Austenite out there that doesn't picture Lizzie and Darcy's marriage as a solid, loving one. And whether Darcy enjoys Mr. B's unannouced visits or not I hardly think he would complain as long as Lizzie was happy. Though I imagine there is some geniuine warm feelings for his wifes father and family (accepting for the Wickhams of course).