CSS resize property
Method of allowing an element to be resized by the user, with options to limit to a given direction.
The status is 'Under Consideration': https://developer.microsoft.com/en-us/microsoft-edge/platform/status/cssresize/
Might also be interesting for SVG elements.
While I'll agree that supporting this as a CSS property across the board would be awesome, the primary concern is for textareas. If this was only added by default for textareas and not even controllable via CSS it would still be a massive improvement over the current textarea rendering... and still be considered a massive success! IMHO. (PS my original textarea only idea request was merged into this one)
They say that "Necessity is the Mother of Invention"... as a result I've provided a jQuery plugin implementation to provide this feature to current Internet Explorer users. It would just be awesome though if Project Spartan supported this natively!
To see a demo or checkout the code see this Github repo: https://github.com/scunliffe/stretchabletextareas (includes a visual demo)