

You are right, basically.
However, the backup solution of Signal will basically export the “content & metadata” of the messages into a re-importable format and then bundle everything into an encrypted container. You will get a separate password for that container file that you need to re-import your messages.
As far as I understand it, Signal will then re-encrypt your messages after the import with the key of your new Signal installation.
It’s called markdown. (More specifically CommonMark)
You can check out the supported syntax by Lemmy HERE. It has a lot of other features available to format text & stuff.