I just don’t think that’s a reasonable expectation of a telecommunications tool, so yeah, I think it’s a fair change well within the norms and expectations of an instant messenger.

You should get to control how/ to whom your data is distributed, but also requiring these recipients to only use software and services of your choosing seems excessive. Platform lock-in at this point seems like the much greater harm.

I could see the case for a small indicator in the contact details that they’re using a third-party client, but anything more (green bubbles?) would be counterproductive.