Lew expresses his own entirely defensible view of things, but others might defensibly differ. In an
Erato thread on the subject, Alicia Stallings said "testing the rules of the sonnet is almost part of the tradition of the sonnet in English (otherwise we'd only have Petrarchan sonnets for one)--and there is practically a whole separate genre of nonce-rimed sonnets, and plenty of sonnets in other meters." And Dick Davis said "I agree wholly with AEStallings - there is a norm and there are variations from the norm."