Do you remember when Facebook bought WhatsApp and they told us that WhatsApp won't be sharing any data with Facebook?
"WhatsApp Will Delete Your Account If You Don't Agree Sharing Data With Facebook"
"In stark contrast, Signal collects no metadata, whereas Apple's iMessage makes use of only email address (or phone number), search history, and a device ID to attribute a user uniquely."
XMPP doesn't need "sealed senders", because it's not a centralized services to begin with.
Good feature sets?
XMPP and all the software around it is well maintained as well. It's also supported AND used by many well known companies.
It's also a lot easier to use. It's also not exclusive in any way. You can use it however you want to use it.
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