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 have a test case on Codepen and have opened up an issue on the SVG github but also posting it here in case anyone knows a more relevant place it should in fact go.
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.