I also came across a link to a book you may have referred to in the past, W. H. T. Dau's Luther Examined And Re-examined.My 2 cents: there are basic hermeneutical problems typical of those who cite this text to summarize the entire Luther.
1. "Sin boldly" comes from a fragment of a letter. It has no address, salutation, or signature. It is not a complete context.
2. "Sin boldly" comes from a letter. It was not intended to be a definitive theological paradigm expressing Luther's full theology, but rather written to a lone individual.
3. Luther was prone to strong hyperbole. It's his style, "sin boldly" is a perfect example. Luther doesn't write analytical theology. He writes profound verbose sentiment driving one to think deeply.
4. Luther had books and sermons intended for a general audience which explains how he parsed out the relationship of faith and works. These books and sermons are not fragments.
Those who cite "sin boldly" typically have little understanding of Luther's theology. These are the type of people that need to be kept out of the jury pool because they're either lazy thinkers, they lack the ability to think critically, or they simply demonize that which they don't like. These are the sort of people who would send innocent people to jail.
So far I've only read the first twenty or so pages and it is an interesting and informative read. It turns out the poster who cranked out the anti Luther stuff for years on the board was just following RC tradition.
I could almost hear Lady Misil saying to me, "So young [in the fath], so naive [about historical Luther hatred]..." Of course, that would be If she were a Christian, still alive, and not saying some writer's lines.