"I'm not really concerned about bugs this can introduce. What I actually find odd is that it's taken me this long to notice. What else would I think "yeah, that should be an error" about, even though I've never actually run into the problem?"
Just an FYI: Arc/Nu does throw an error, because it uses Racket's optional-arg support. And even when it needs to fall back to full-blown destructuring, it still throws cryptic errors rather than doing nothing.
