Kellan: " '… and that’s not my code.' ouch"
Eric: "Right now, the only thing we have special for Magpie RSS is that we don’t serve Atom to that user-agent if the version is 0.5."
Rasmus: "I wrote a simple little PHP 5.1-based RSS parser a while back and it doesn’t have any problems with that ... feed."
Source: Comments on my previous post
Facepalm, headdesk. As it turns out, the issue I was having with my PHP XML parsing was that I was trying to cram raw gzip streams down its throat, caused by some odd things I was trying to do with HTTP headers copied cargo-cult style from a Python module I've tried reinventing in PHP.
In other words, completely braindead work by someone who should know better, even though he's relatively new to PHP—where he is defined as me.
But, kudos to the people of the lazyweb for taking the time to triangulate me and remove all doubt within scant hours of my post. Not counting a half-dozen private emails, I got very quick responses from the author of MagpieRSS, the CTO of FeedBurner, and the creator of PHP himself—each very nicely, clearly, and rightly saying:
"...and that's not my code."
Be careful when you attempt to invoke the lazyweb, because it might just respond!