Does Select2 allow for changing name of "text" key to something else?

Changing my js to the following sorted the issue:

function format(item) { return item.description; };

$scope.select2Options = {   
    simple_tags: false,
    placeholder : "Search for a language",
    multiple : true,
    contentType: "application/json; charset=utf-8",
    minimumInputLength : 3,
    data:{ text: "description" },
    formatSelection: format,
    formatResult: format,
    ajax : {
        url : "/bignibou/utils/findLanguagesByLanguageStartingWith.json",
        dataType : 'json',
        data : function(term) {
            return  {
                language : term
            };
        },
        results : function(data, page) {
            return {
                results :
                    data.map(function(item) {
                        return {
                            id : item.id,
                            description : item.description
                        };
                    }
            )};
        }
    }
};

Notice: one has to use the Select2 top level attribute data.

Select2 requires that the text that should be displayed for an option is stored in the text property. You can map this property from any existing property using the following JavaScript:

var data = $.map(yourArrayData, function (obj) {
  obj.text = obj.text || obj.name; // replace name with the property used for the text
  obj.id = obj.id || obj.pk; // replace pk with your identifier
  return obj;
});

Documentation

Here's the bare minium of the configuration neccesary to use a custom id and text properties on ui-select2

$scope.clients: {
  data: [{ ClientId: 1, ClientName: "ClientA" }, { ClientId: 2, ClientName: "ClientB" }],
  id: 'ClientId',
  formatSelection: function (item) { return item.ClientName; },
  formatResult: function (item) { return item.ClientName; }
}