For the western emacs user probably not much. Unfortunately, the ability to use non-latin typefaces in the apps are often (resasonably) neglect by most devs.

Using HarfBuzz (that is a font shapping library), the dev don't have to worry about how the text is going to look in other languages, such arabic, chinese, etc. The library will take care of that.

HarfBuzz is the same text engine used by Firefox and XeLaTex.

Also it allows the user to use features such ligatures, font weight, emojis. Not sure if emacs will support those from the start.