… No, you don’t get it.

Every time a Signal user would send a message to WhatsApp, they’d be leaking metadata to WhatsApp, because WhatsApp would create and store metadata from the Signal message it recieves, which would make the Signal user insecure, less secure, because WhatsApp will sell that data to data brokers or provide it to the government if requested.

This represents a loss of privacy and security to Signal users, not an increase.

… Also, Signal is not actually 100% foss, it uses some closed source, Google provided components.

Molly FOSS is a fork of Signal that replaces these Google components with fully foss ones.

…

You keep acting like Signal has some need to expand its market share, and that the best way to get it to do so is by abandoning its core, primary feature, the reason people use it.

Signal will likely never do this, because they are interested in security and privacy, not comprimising security and privacy in hopes of gaining popularity and market share.

Again, see the comic I already linked.

You are demanding that two incompatible things be made compatible because one of them is better, but you fundamentally do not understand that making them compatible will make the better thing as bad as the worse thing.

You can fit the square peg into the round hole, but only if you shave down the square peg into a cylinder, at which point, you no longer have a square peg.

If you got your way and Signal could message WhatsApp, and then you started using Signal to just only talk to WhatsApp users, you might as well just be using WhatsApp to talk to WhatsApp users, it would be the same level of (in)security.

This would also make no sense for Signal to do because it would make their own software pointless, just an alternative gateway to WhatsApp, with less features than WhatsApp and less security than it had before.

…

If you wanna make a Signal fork that can interoperate with WhatsApp, go right ahead, no one is stopping you.

Set up a clone of the Signal repo, setup a WhatsApp business account, purchase access to WhatsApp’s API, host and pay for your own servers to manage the WhatsApp end of the system, and write your desired interoperability features into your Signal fork, then release it as an app for android, iOS, macOS, windows and linux.

Here’s an intro to the WhatsApp API:

https://nativemsg.com/resources/text-marketing/the-ultimate-guide-to-whatsapp-api-everything-you-need-to-know/

Here’s the Signal repo:

https://github.com/signalapp

Best of luck!