[Baertram]

zo_strformat("<<1>>", player) is just removing any special gender suffix ^f e.g. at the end of the character name.
And I guess the ZO_LinkHandler will just use the @displayName in the link and if you click it use the @displayName as well.
As you can see here:
https://github.com/esoui/esoui/blob/...ndler.lua#L100

function ZO_LinkHandler_CreatePlayerLink(displayOrCharacterName)
    if(IsDecoratedDisplayName(displayOrCharacterName)) then
        return ZO_LinkHandler_CreateDisplayNameLink(displayOrCharacterName)
    else
        return ZO_LinkHandler_CreateCharacterLink(displayOrCharacterName)
    end 
end

It would be using ZO_LinkHandler_CreateDisplayNameLink then as the @ is given in the name.

Afai found out Shadowfen is completely correct here.
You would need any kind of "lookup" tables which are given if you are in the same group/guild.
Else you'd have to build and safe your own lookup tables for the server and enhance it each time someone writs with a charactername in chat.
And I would not recommand doing/building such a big table. It will grow your SavedVariables and make every loading screen slow after a short time already, as the filesize would grow constantly and would need a transfer to file/read from file on each reloadui/zone change/login/logout.