One of the complaints about Signal is that although the content is encrypted end to end, the sender and receiver are in the open. This is analogous to a postal service letter where the contents are unviewable. Signal now offers something to obscure the sender (like not putting a return address on a letter), but the receiver must be known to the servers in order to properly deliver it.

Although the Signal protocol is probably sent to the Signal servers encrypted, privacy enthusasts contend that it's possible that the maintainers of Signal could be coerced into providing the sender and receiver of messages, even if the messages are not viewable.

Probably because a phone number isn't required!?

Signal has much work to do to be a real "privacy" app. Get rid of phone numbers, get rid of metadata, stop contact mining. They say they don't mine contacts but it is easy for them to do if they wanted to, so I assume they do.

Tor is great but has speed issues and no udp, so no voip. A lot of room for improvement there also. We should welcome all that try to improve on what we have.