Some background:
Signal chats are pretty popular in Germany among communities that do not want to use Facebook groups, Whatsapp or commercial tools like Slack or Threema (Threema – Secure Communication For Individuals and Companies – Threema). One reason (at least for the META Tools and Slack) are privacy concerns.
These communities often use Signal chats for group communication instead. But they also understand that such unstructured “short time” communication is not the right solution for “serious” group collaboration when you have a group of more than 20 people …
If notifications from signal could be duplicated into a discourse thread somehow, this would support either a soft migration from signal to discourse or some kind of parallel operation. All in all, it would make the migration to Discourse easier and create more user acceptance.