Everybody was in the wrong here. The developer should've written better code. I'm a PHP developer and I've learned that if the input is that important, I need to cast it. I've used C++, C#, and Java and I like strict typing. If your application is that sensitive then maybe it should've casted the input to ensure the output is consistent.
As for Rasmus, I think he could've explained why it's a "won't fix" type bug in a slightly more diplomatic fashion, though I can't say I would've handled it any differently. He's completely right as to why the behavior shouldn't change. Finally, bjori's response was completely unnecessary, inflammatory, and downright rude.
This has shown me the worst of the PHP community. I'm not ashamed, just more wary.