I can't remember where I read it, but it seems the Austen family as a whole had a prejudice against the name "Richard", and were convinced that anyone by that name would eventually turn out to be less than worthy... So, when JA described "a thick-headed, unfeeling, unprofitable Dick Musgrove", she may have been describing the *name* (in an in-joke to her family) rather than a particular person (though of course I'm sure she could think of more than one example who could be the pattern for Dick!)