But a primary with a crappy seal? Haven't heard that discussed much. The bad seal thing could, theoretically, lead to oxidation. My guess is that it's probably (a) not a huge deal unless it's REALLY bad, and (b), if your kit came with a primary with a crappy seal, it probably came with a bunch of other crappy stuff too, and it's not going to matter if you move to secondary. And even then, plenty of breweries used open top-fermentation throughout history... Those are just guesses, I'd be interested to hear more.