I dont think that he's meant ot be a "real character" - he is (like Mr and Mrs Bennet) to be a caricature of a young man who having married and found that his wife is a complete idiot, consoles himself by being awfully rude to her and to everyone else...Its meant to be funny, not entirely realistic, (like an "idiot" character in a sitcom such as Joey in Friends) but in the later part of hte book I think that Austen had to make Palmer a bit more nice and pleasant and helpful, but it doesn't sit very well with the earlier caricature Mr P.

Soemthing similar I think happened with Mrs Jennings who in the first part of the book is rather a caricature of a gossippy, often foolish, vulgar woman who may mean well but also does harm by hre lack of senstiivity, and who is also so vulgar that the Dashwoods find her very tiring... |But in the later part when Marianne becomes ill, we are shown Mrs J being so good and kind and helpful that "ELinor really loves her"....