This is superb! I have a small tool with a web frontend, that I use a specific emoji to represent but I didn’t have a favicon yet, because if I used a PNG of an emoji that Apple made I’d be infringing on their copyright.
Using SVG and having the browser and OS provide the rendering of the emoji is perfect for the favicon of my tool!
A quick search says it's possible to get the PNG data URL from a canvas. I wonder if it's viable to draw an emoji to a canvas, and extract the PNG out of it for the favicon.
Would a lawyer go after "client-side copyright infringement"?
Emoji, anywhere with text. If you mean favicon, you can see them in different places, but one example is top left of the tabs if you are using the device in landscape. If you mean desktop Safari then I don't remember as I don't use it on desktop.
This site has a nice one-click copy button for each "emojicon": https://emojicon.dev/