> It's not a way to make sure you can identify the outgroup and shun them; it's a meaningful signal of what technology other people you're chatting with are using, which tells you useful information about their capabilities.
That seems like a false dichotomy to me as those are not mutually exclusive, and indeed can (and are) both easily accomplished with the current system.
Apple does not in any way intend it to be used to identify the outgroup and shun them.
SMS on the iPhone used green bubbles for years before iMessage existed. When iMessage was introduced, it had blue bubbles simply to distinguish it and make clear "these are users of the new service you can video chat with, send files to, etc". Like I said: a useful informational signal.
It wasn't until years after that that this wailing and gnashing of teeth about blue vs green bubbles started. To the extent that such a social dichotomy exists, it is a purely emergent socially-created one, not one that Apple has pushed in any way.
Furthermore, it would be a regression for Apple to remove that useful informational signal just because people are upset that they get accurately identified as "the one in the group who is using a different device, and thus cannot safely be added to group chats for reasons entirely outside of Apple's control".
The bubble color isn't the problem. The problem is, as you somewhat allude to, inseparable from the fact that there is a way to tell the difference between People Using iMessage on Apple Messages and People Using SMS.
That seems like a false dichotomy to me as those are not mutually exclusive, and indeed can (and are) both easily accomplished with the current system.