Better image scaling. No more jaggies for downscaled images!
Responsive websites typically send a larger version of an image and then scale it down to match the available space on-screen. This is especially important in mobile when the user can change screen sizes without a reload by changing from portrait to landscape, for example. Even the Microsoft websites utilize this kind of responsive design.
What does this have to do with IE? Well if you do this with IE the insane image scaling will provide images so jagged even the largest fonts become unreadable.
In earlier versions of IE we could use a nonstandard CSS property to switch to Bicubic scaling, but that property was removed!!
I run an art site, Inkbunny, where we regularly have 4K-to-8K artwork displayed in a "wide" mode with width:100% scaling. This is great except that Edge's resizing is aliased and actually falls over sometimes without any error message (just showing a blank white image).
This might be related in part to their use of hardware-accelerated decode.
However if that's just the decoding it's hard to see why the rendering can't be done better.
Philipp Wolfer commented
Yes, it is not quite clear to me why support for CSS image-rendering has been set to low priority on https://dev.windows.com/en-us/microsoft-edge/platform/status/?filter=f3f0000bf&search=image-rendering
At the very least Edge should apply a nicer algorithm for image scaling by default, as other browsers do, too.