As you say, seeking out Elizabeth to go walking with her must have seemed terribly "encouraging" to the man who back at Netherfield hardly spoke to her at all on her last day for fear of raising her hopes! You persuade me more and more that Darcy had already made up his mind. I don't know, though, if he really thought he was "courting" Elizabeth or if he thought that merely indicating his willingness was courtship enough from a man like him! ;-)