When @-user-mentioning in a group, the user mention link uses the text set for a contact, but not the public name set by that user.
It may be the serious vulnerability risk of exposing of the name of that user.
Let's say the user uses the name "Somebody anonymous", but then I add that user to my contacts and set their name to "John Smith". And now, each time I mention that user in a group chat, their name-link is displayed as "John Smith" for everyone who sees that link, but it should be displayed as "Somebody anonymous".
It doesn't depend on device
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However, this isn’t really a privacy issue for the app to solve, as it allows you to link to a user with arbitrary text. A person can just change the mention link from the username to their real name pretty easily.
If anything, having the option for a user to set the default mention text (either to something specific or to allow to use other user’s contact names for that user) for a specific group is a convenience feature (and one I would very much like to see added)