Signal doesn't achieve this at all. In this regard, they are just another messaging service that's not compatible with anything and also they are discouraging (

Signal doesn't achieve this at all. In this regard, they are just another messaging service that's not compatible with anything and also they are discouraging (to say the least) unofficial clients from connecting official servers. They are yet another fragment in the already fragmented ecosystem. What's a step forward in this regard is projects like libpurple or Matrix bridges. Whose goal is to make already existing networks interconnected.