Comedy must be transgressive. It must cross borders we would never dare to. That's what makes us laugh -- that moment of terror when a taboo is violated, and immediately that taboo is turned into silliness.
Cary Grant threatening to kick a woman in the teeth crosses borders, alright.
His Girl Friday rampages across the conventions of romantic love, giggling at its own cleverness and moving far too fast to ever sink into its own depths.
This is a good thing. Comedy does not require study or introspection. The ultimate transgression is to refuse to take seriously the most profound matters -- which is why so many great jokes revolve around death or love. His Girl Friday takes on both with gleeful abandon.
It does it in the context of two couples, both kept apart. Hildy and Walter, separated by their own pride and stubborness and blindness, and Earl and Molly, separated by cell bars and the gossip of the press. But where Hildy's and Walter's pain is a springboard for laughs, Molly and Earl are the straight men. They aren't witty or ambitious or good-looking, but (or perhaps and therefore) their love for each other is as simple and pure as such a thing can be. It's not even romantic love but simply the compassion of one person for another.
And when tragedy strikes Molly, all the newspapermen can do is lean out the window and watch. But there is no laughter n the audience at that moment. Tragedy of course strikes Hildy and Walter unrelentingly, but it's always funny tragedy, ridiculous, never given the seriousness we're more properly told it deserves. And by contrasting their farcical melodrama with the tragedy of Molly and Earl, this film sets us up to wonder about the relationship between pain and humour.
Great comedy always shows us pain. It's by taking pain and mocking it, twisting it into foolishness, that we create humour, which is why the greatest comedy is always the blackest. It's the truest. And the truest moments in His Girl Friday come when the pain between Hildy and Walter is at its highest, and the story refuses to let us share it with them. Every time poor Bruce calls with another story of how he's been duped, every time Hildy tells Walter how poorly he treated her, every time Walter throws her devotion back in her face, we get another laugh. And yet again we're denied the "tragic" release of commiseration, and instead offered the "comic" release of wit.
Famous quote from Mel Brooks: "Tragedy is when I walk into an open sewer and die. Comedy is when YOU walk into an open sewer and die."
Another Steph and Core theory: Stories ask their audience to either identify with the protagonist or sympathise with them -- either you want to be them, or you understand them. Stories that offer only identification don't have much to offer people who have already looked within themselves and faced their darker corners. Stories that offer sympathy are always relevant, for we are always needing to acquire more understanding about our fellow folks.
Comedy is by its nature a creator of sympathetic stories. Nobody wants to BE Walter or Hildy, but we certainly understand them.
And when Cary Grant tells that woman off, we kind of admire him, too.