Oh, not supporting emojis is understandable. I think it still shouldn’t crash like that, and it’d be nice if it rendered unsupported characters (even when composed of surrogates) as “<?>” or something.
I already happily use quads for non-user-defined text, and I’m working on restricting/filtering user-defined text now. It’s a little unfortunate to have to ban all emojis from usernames and in-game chat. Even only supporting the most common emojis, and an API for querying whether a given string is fully supported, would IMO be quite useful.