Cool to see you guys using the polyfill. We created that so we could get Designer launched. At the time we were told it might be months until the Jetpack Portfolio would be available, meanwhile we were already using the Portfolio on WordPress.com. So we forked the WordPress.com version and built in a few tidbits. Mere days after we launched Designer they shipped the Jetpack Portfolio. Sigh. ;)

So we've just been using Jetpack since they launched it. Sorry for the outdated reference to the polyfill in that Designer doc.