Requested feature overview description.
Scalable Vector Graphics is an image format for two-dimensional vector graphics with support for interactivity and animation.
Why would it be useful?
Users can upload vector graphics instead of a superabsurd_res raster version.
What part(s) of the site page(s) are affected?
Upload.

https://e621.net/forum/show/270871

TLDR: has the same security issues which are preventing HTML5 support from being implemented. Also problems with non-embedded image files, if the SVG happens to use this feature.

Also: use the search. this thread was right there on the 1st page of results for 'svg'