Custom text binding handler
You can call it more directly using this:

return ko.bindingHandlers.text.update(element, valueAccessor);


The valueAccessor is already a function that returns the value, and update already uses unwrap internally, so there is no need to use the inline function.

Or more safely, preserving the other arguments to the handler, you can call it like this:

return ko.bindingHandlers.text.update.apply(this, arguments);


However, wrapping text binding handler is better done with a preprocessor, to ensure that other parts of the binding lifecycle are handled normally.

ko.bindingHandlers.line = {
    preprocess: function (value, name, addBinding) {
        addBinding('text', value);
        return value;
    },
    update: function (element, valueAccessor, allBindings) {
        if (ko.unwrap(valueAccessor())) {
            $(element).after('&lt;br /&gt;');   // Make the element invisible
        }
    }
};


Here is a fiddle.