Twitter isn't the messenger. This is what they want you to think. Twitter is a private, for profit company. It's not a public place lake the street. They have to be proactive and follow the local laws. They are responsible for what you can read on it as well as the people posting.
This is a huge difference with the street. The street is public not private, you're responsible for what you say.
Internet is not the wilde west. Companies have to follow and adapt to the local law or just not operating there.
It doesn't double the capacity. It's more a 30% increase. And, double-deckers are actually old. They date from the 19th century. In 1855, the Chemin de fer de l'Ouest introduced double-deckers on suburban lines of Paris.
https://fr.wikipedia.org/wiki/Voiture_Ouest_%C3%A0_imp%C3%A9riale
Modern double-deckers date from the 1930s, with the Voiture à étage Etat:
https://fr.wikipedia.org/wiki/Voiture_%C3%A0_%C3%A9tage_%C3%89tat