Luther Admitted He Was Not Following the Rules of Language When He Translated Romans 3:28?

Here's a Martin Luther-tidbit from one of Rome's defenders on the CARM boards:

You do realize that Luther admits that he didn't add the word alone due to the rules of language but because he said that is what Paul meant to say. That's Luther's own admission, so yes, Luther added the word alone so that it read like what he thought is should say. So much for a person who held Scripture in such high regard.

And also:

In his An Open Letter on Translating: "So much for translating and the nature of language. However, I was not depending upon or following the nature of language when I inserted the word "solum" (alone) in Rom. 3 as the text itself, and St. Paul's meaning, urgently necessitated and demanded it." Luther inserted his own theology into the text.

And also:

As I have stated already, Luther admits he did not use the rules of language as the basis for adding the word alone. "However, I was not depending upon or following the nature of language when I inserted the word "solum" (alone) in Rom. 3 as the text itself, and St. Paul's meaning, urgently necessitated and demanded it."

And also:

All of your appeals to the German language mean nothing because Luther freely admits, as I have quoted, that he was not following the rules of language when he inserted the word alone. He did it because he believed that Paul meant to say alone.

The polemic is blatant: Luther is said to have simply added the word "alone" to Romans 3:28 to fit his theological agenda. The basis for this is a statement Luther himself made,  "I was not depending upon or following the nature of language when I inserted the word "solum" (alone) in Rom. 3 as the text itself." let's take a look at this quote and see if it substantiates this typical Roman Catholic narrative.

Documentation
The sentence is said to come from Luther's An Open Letter on Translating. This refers to a document Luther wrote in 1530 which covered the topics of justification by faith alone, his methodology in regard to his German translation of the Bible, and the intercession and prayer to the saints. This document was originally written in German, "Ein sendbrieff D. M. Luthers. Von Dolmetzschen und Fürbit der heiligenn" (WA 30 II, 627-646). The comment can be found on page 640:

As far as I can tell, the English rendering of the sentence being utilized was taken from a version originally put up on the Project Wittenberg website. Project Wittenberg has been around for quite a few years now. This website was up and running years before the onslaught of Google Books. At one time, it was one of the few places one could go to read Luther's writings online in English. Some of the versions of Luther's texts on Project Wittenberg appear to be unique to their website. Their version of An Open Letter on Translating, was put together by Gary Mann, Ph.D. Assistant Professor of Religion/Theology Augustana College Rock Island, Illinois. Mann's translation reads,

So much for translating and the nature of language. However, I was not depending upon or following the nature of language when I inserted the word "solum" (alone) in Rom. 3 as the text itself, and St. Paul's meaning, urgently necessitated and demanded it. 

Mann's English translation is not the only one available. One of the most enduring translations was that done by Charles Michael Jacobs in the Philadelphia Edition of Luther's Works (PE 5:10-27). This translation was revised by LW 35:175-200. In PE 5, the comment can be found on page 20. In LW 35, page 195. For the context, Mann's translation will be used below.

Context

So much for translating and the nature of language. However, I was not depending upon or following the nature of language when I inserted the word "solum" (alone) in Rom. 3 as the text itself, and St. Paul's meaning, urgently necessitated and demanded it. He is dealing with the main point of Christian doctrine in this passage - namely that we are justified by faith in Christ without any works of the Law. In fact, he rejects all works so completely as to say that the works of the Law, though it is God's law and word, do not aid us in justification. Using Abraham as an example, he argues that Abraham was so justified without works that even the highest work, which had been commanded by God, over and above all others, namely circumcision, did not aid him in justification. Instead, Abraham was justified without circumcision and without any works, but by faith, as he says in Chapter 4: "If Abraham is justified by works, he may boast, but not before God." However, when all works are so completely rejected - which must mean faith alone justifies - whoever would speak plainly and clearly about this rejection of works would have to say "Faith alone justifies and not works." The matter itself and the nature of language necessitates it.

Conclusion
Whatever English translation one uses, Luther does provide reasons as to why he used the word solum in his German translation. Luther's intention was to translate the Bible into an easily comprehended form of popular German. His translation at times employed dynamic equivalence (as many translations do). Word-for-word translations can be cumbersome and awkward, and can miss the thrust of the original thought. Rather, many translations seek to maximize readability with a minimum of verbal distortion by translating according to “concept.” In translating Romans, Luther tried to present the impact of what the original Greek had on its first readers, and to present the German style and idiom equivalent for his readers.

An honest translator, Luther freely admitted the word “only” does not appear in the original Greek at Romans 3:28. He states, 

Here, in Romans 3[:28], I knew very well that the word solum is not in the Greek or Latin text; the papists did not have to teach me that. It is a fact that these four letters s o l a are not there. And these blockheads stare at them like cows at a new gate. At the same time they do not see that it conveys the sense of the text; it belongs there if the translation is to be clear and vigorous. I wanted to speak German, not Latin or Greek, since it was German I had undertaken to speak in the translation. But it is the nature of our German language that in speaking of two things, one of which is affirmed and the other denied, we use the word solum (allein) along with the word nicht [not] or kein [no]. For example, we say, “The farmer brings allein grain and kein money”; “No, really I have now nicht money, but allein grain”; “I have allein eaten and nicht yet drunk”; “Did you allein write it, and nicht read it over?” There are innumerable cases of this kind in daily use.

In all these phrases, this is the German usage, even though it is not the Latin or Greek usage. It is the nature of the German language to add the word allein in order that the word nicht or kein may be clearer and more complete. To be sure, I can also say, “The farmer brings grain and kein money,” but the words “kein money” do not sound as full and clear as if I were to say, “The farmer brings allein grain and kein money.” Here the word allein helps the word kein so much that it becomes a complete, clear German expression. (LW 35:188-189).

Granted though, Rome's defender has seized upon Luther's seeming admission that he "was not depending upon or following the nature of language when I inserted the word "solum" (alone) in Rom. 3." This does seem like a blatant denial of the syntax and grammar of the original text. The solution comes by looking carefully at the original German text and other English translations. The German text of this sentence reads in part, "Aber nu hab ich nicht allein der sprachen art vertraut und gefolgt, daß ich Röm. 3, 28. solum (allein) hab hinzugesezt; sondern der Tert und die Meinung Pauli fodern und erzwingen es mit Gewalt." (WA 30 II:640). LW 35:195 translates this as, "Now I was not relying on and following the nature of the languages alone, however, when, in Roman 3[:28] I inserted the word solum (alone)." PE 5:20 translates similarly, "Now however, I was not only relying on the nature of the languages and following that when, in Romans iii, I inserted the word solum, 'only,' but the text itself and the sense of St. Paul demanded it and forced it upon me." Luther is saying that he did not only follow the nature of the language, but also saw the thrust of the text demands using "alone."

The need for "alone" in Romans 3:28 was not unique to Luther. Luther mentions others before him translated Romans 3:28 as he did (for example, Ambrose and Augustine). The Roman Catholic writer Joseph Fitzmyer verified Luther’s claim and also presented quite an extensive list of those previous to Luther doing likewise. Even some Roman Catholic versions of the New Testament also translated Romans 3:28 as did Luther. The Nuremberg Bible (1483), “nur durch den glauben” and the Italian Bibles of Geneva (1476) and of Venice (1538) say “per sola fede.” It is entirely possible Luther’s understanding of “faith alone” differs from those before him, but that is not the issue. The issue is whether or not the thrust of Romans 3:28 implies “alone.” Others previous to Luther may have differed in theological interpretation, yet saw the thrust of the words implied “alone.” Hence, as a translator, Luther holds company with others, and cannot be charged with a mistranslation. If he’s guilty of such a charge, so are many before him.