On which so many discussions turn is simply this: "What IS the Church?"
How one answers that determines so much! The Lutheran Symbols provide our answer to the question in the Apology. "But the Church is not only the fellowship of outward objects and rites, as other governments, but at its core [principaliter], it is a fellowship of faith [societas fidei] and of the Holy Spirit in hearts." Ap VII/VIII:5
If one grants this, then it is clear why the so-called canonical boundaries [societas externum rerum] are only proximate. There are those within given canonical boundaries that do not partake of the Church's true inner life, her society of faith and the Holy Spirit in the heart. And there are those outside given canonical boundaries who do partake of her inner life, her society of faith and the Holy Spirit in the heart.
This means, it seems to me, that a Lutheran cannot and will not identify the Church itself with any canonical jurisdiction. The Church herself, to whom the promise has been given that the gates of hell will not prevail against her and that she is the pillar and ground of the truth, is not principally this or that jurisdiction, but: "people scattered throughout the whole world. They agree about the Gospel and have the same Christ, the same Holy Spirit, and the same Sacraments, whether they have the same or different human traditions." [Ap VII/VIII:10]
When the charge is leveled against this notion that it's mere "idea" - the Apology answers: nonsense! It's not an idea, a platonic state, "But we do say that this Church exists: truly believing and righteous people, scattered throughout the whole world. We add the marks: the pure teaching of the Gospel and the Sacraments. This Church is properly the pillar of the truth. For it keeps the pure Gospel." [Ap. VII/VIII:20]
So when the talk of Church arises, the very first question is NOT "visible or invisible" or any other such thing. The first question is: what do you mean by Church? Until we get that through out heads, we're just talking past each other.