I think this was funny and yet... I know of a real life situation like this... sort of. My college housemate's mother turned down her live-in lover's marriage proposal several times...The first time because he didn't have a ring when he asked, the second because the ring was too masculine, the third because the diamond was too small and the fourth because he didn't make enough effort to make it romantic (he was by that time fed up and it showed).
They broke up. So I'm happy Severus and Harry made it!
I also think it was a very sweet proposal. (That snake thing though might have been doomed to fail. Even if the snakes understood what he said, would Harry have understood Keats?)