I mentioned earlier that at Marburg Luther and Zwingli spoke very different dialects of German. Luther, always the pugnacious soul, never did ‘let it go’ (he never let anything go). In 1544 Luther wrote-
In our age God has appointed matters in such a way that the devil is prevented from speaking good German; that is how Karlstadt and Zwingli had to talk, so that it cost me much labor to understand what they were saying.*
Luther, it seems, felt the same about his kind of German that the KJV Only crowd feels about the KJV.
*Preface to Justus Menius, on the Spirit of the Anabaptists: 1544. Luther’s Works (Vol. 60, pp. 333–334).