Hester

I have read, though not yet entirely verified to my satisfaction, that the Harlequin costume of coloured diamonds originated in the rag costume (still used by some mummers), being a stylised version.

If that's so, some linking of Harlequin with the mediaeval figure may well be in order. You have to remember that Commedia Dell' Arte is very stylised though, and undoubtedly Harlequin came from more than one original stereotype, so I wouldn't read too much into the connection.

As regards Punch, earlier versions of the show call him Punchinello and the history is quite well documented. Here's one of the very good history pages on the web. Here's another one ...

:-)
Ian