See ["How do comment @replies work?"][1] and ["@Peter works for Péter Török?"][2].

Comment replies *will* often work with unicode. EG: Péter Török can be reached by both `@Peter` and `@Péter`.


----------
These are the *documented* rules (Not checked against latest source) for converting user `display_name` to comment-reply `@names`:

 1. Remove any spaces.
 2. [Single quotes, dots, dashes and underscores should **not** be removed.][3]
 3. [Special characters are replaced with their simple equivalent.][4]  
  The rules for that were last documented in [this answer from Jeff Atwood][5].  For convenience the last posted remap code was:


<!-- language: lang-c# -->

    public static string RemapInternationalCharToAscii (char c) {
        string s = c.ToString ().ToLowerInvariant ();
        if ("àåáâäãåa".Contains (s) ) {
            return "a";
        } else if ("èéêëe".Contains (s) ) {
            return "e";
        } else if ("ìíîïi".Contains (s) ) {
            return "i";
        } else if ("òóôõöøoð".Contains (s) ) {
            return "o";
        } else if ("ùúûüuu".Contains (s) ) {
            return "u";
        } else if ("çccc".Contains (s) ) {
            return "c";
        } else if ("zzž".Contains (s) ) {
            return "z";
        } else if ("ssšs".Contains (s) ) {
            return "s";
        } else if ("ñn".Contains (s) ) {
            return "n";
        } else if ("ýÿ".Contains (s) ) {
            return "y";
        } else if ("gg".Contains (s) ) {
            return "g";
        } else if (c == 'r') {
            return "r";
        } else if (c == 'l') {
            return "l";
        } else if (c == 'd') {
            return "d";
        } else if (c == 'ß') {
            return "ss";
        } else if (c == 'Þ') {
            return "th";
        } else if (c == 'h') {
            return "h";
        } else if (c == 'j') {
            return "j";
        } else {
            return "";
        }
    }


  [1]: http://meta.stackexchange.com/a/43020/148310
  [2]: http://meta.stackexchange.com/q/48968/148310
  [3]: http://meta.stackexchange.com/a/51913/148310
  [4]: http://meta.stackexchange.com/a/49409/148310
  [5]: http://meta.stackexchange.com/a/7696/148310