As for your bottom line remember the contributors are working on it for free, they are not selling anything. So they are not running after more users. It’s good as it is, non technical people can use flatpack or AppImage and technical people can add a repo without issues.
And someday someone could add it to the official repo, it could be you.
The only relevant part in that link is this:
Some third-party repositories might appear safe to use as they contain only packages that have no equivalent in Debian. However, there are no guarantees that any repository will not add more packages in future, leading to breakage.
And you should be safe about this.
As I was saying, the devs are not responsible for including the package to the official repo. You are owed nothing and have plenty of other options to install it.
Adding a repo is not “tainting” an install. Adding a package to the official repo is not the responsibility of the devs but of Debian’s package maintainers.
Because stripping files metadata is an expected features for a messaging client. Not for the network like you described but for the client.
That’s actually vx-underground source for this post: https://xcancel.com/vxunderground/status/2032562782248349793#m