Well now I'm confused. I've always received SMS as fallback when my contacts add me to RCS group messages. But apparently this doesn't always work according to people on the internet at large?
Unfortunately most people still think they're "texting" and have no idea Google and Apple pulled a bait and switch. Meanwhile on my end I receive emoji react spam, each emoji as an independent message, in an incredibly verbose form that quotes the entire message.
It's simultaneously misleading people, a DoS against non-BigTech clients, and monopolistic. The mobile ecosystem just keeps getting worse and there's no sign of regulations fixing it any time soon.
That said, I have no idea how often that fails in practice.
And that is how reactions are sent in SMS/MMS. Your app just isn't recognizing them to display them nicely. Maybe try a different one?
Imagine if IRC clients started adding such functionality. Certain protocols and conventions are useful precisely because of their minimalism.
Google and Apple are already running their own walled off proprietary messaging platforms. There was no need to tamper with SMS.
But since RCS has become such a mess, and is so anti-competition (you can't make your own app, or servers), I think the answer is now extremely clear: don't use your telecom's messaging system at all, they are all by far the slowest, least reliable, and least private option. App-based messaging is better in almost all practical cases, and I think it's also a healthier future to head towards.