Browsers are not handling emoji in SVG text elements equally. I’m not saying correctly here because I believe it’s an area that the spec doesn’t cover. Because emoji are multicoloured there’s no defined way of handling them in combination with several SVG text properties such as stroke and fill.
I haven’t opened any browser bugs yet as it’s not yet obvious which is the correct behaviour. As I mention in the Github issue a combination of the behaviour in Edge and Chrome feels the most correct.