Earlier quoted context omitted.
The thing about IE, one thing anyway, is that it's CSS support, box model, etc, was broken and non standard. So you would need to exploit CSS parser bugs to give IE a separate CSS, use DXImageTransformFilter to make png transparency work, etc. Maybe by WebKit you mean Blink and by Blink you mean V8, because when somebody does a "Show HN: something that doesn't work in Safari or FireFox" it's usually a javascript prob…
That DirectX filter hack for PNG transparency haunts me. What makes it so much worse is that Tasman, the engine used in IE for Mac, had awesome support for CSS, transparent PNGs, and more years earlier, but for some reason it got dumpstered when IE for Mac was discontinued while the inferior Trident lived on in Windows.
Even thinking of that makes me very happy I haven't had to worry about formatting email newsletters for more than 10 years now, brings back bad memories...