Franzenism

I haven't read the book (or the included essays) myself, but in the TLS review of Jonathan Franzen's new non-fiction collection there is a weird notion quoted:

"In an uptight essay entitled 'Comma-Then', he announces that one of the best reasons a writer can give him to 'put a book down and not pick it up again... is to use the word then as a conjunction without a subject following it."

I too can be offended by small things like that, but the extravagance of the reaction aside, what exactly does he mean?  A sentence like "He killed it, gutted it, skinned it, and then cooked it for dinner"?  It should be "then he cooked it"?  I think my own writing is pervaded by this purported atrocity, though the usage is a little hard to look for.