Polymer's paper-input element allows two way binding of value attribute when used with shady DOM. But it does not allow two way binding with Polymer 2 because Polymer 2 uses shadow DOM
<paper-input label="User Name" value="{{username}}"> </paper-input>
There is a possible explanation here https://github.com/PolymerElements/paper-input/issues/297
But I am not sure if I understood it correctly or I am missing something. It is little hard to believe that paper-input was never intended to be two way bindable?
<paper-input>
works with two way binding. Tested with Polymer 2.
b.t.w. The github issue was closed over a year ago...