[johnmorrison]

> This has proven to result in an unacceptable user experience... Worse, it is dangerous. If you send me a message and I respond to your message with some thumbs-up emoji, and your platform doesn't support it ... that information gets lost. You believe I have disregarded your message. You may assume I have been rude when the opposite is true. This is absolutely unacceptable UX.

This is an assumption that bad implementation is the only possible implementation, and it is wrong.

Obviously omitting content from missing features is bad UX - but it's absolutely not necessary to interoperate. It's easy (and should be expected) to avoid this by simply telling the user something from a missing feature has been sent - they can then inquire and get back the lost information / clear up the confusion.

Furthermore if interoperability is implemented on both ends, the sender's client should know to alert the sender before they attempt to use features missing on the receiver's end.

None of this is a difficult issue.