So I have yet to feel that I have a firm grasp on how the indicative and subjunctive moods work in Latin concessive clauses. I know that many grammars and prose composition books state that "in the best authors" certain concessive conjunctions take certain moods (quamquam = indicative, quamvis, licet = subjunctive, etsi, etiamsi, tametsi, ut = either), and I know that "later authors" don't follow these conventions as closely.
What I therefore have a question about is the difference in nuance that is conveyed by indicative and subjunctive concessive clauses. What makes the most logical sense to me is that indicative concessive clauses concede something as a fact, while concessive subjunctive clauses concede something for the sake of argument.
Some grammars/prose composition books agree with this (North & Hillard Prose Composition §29), while some claim that subjunctive concessive clauses can (particularly in authors such as Tacitus) also concede FACTS (Woodcock §244-§249). Given that I largely conceive of the subjunctive mood as being "not the indicative mood", I am desperate to understand why a subjunctive concessive clause would concede a fact. I will be very happy if I can be told that this is not the case.
Or alternatively, even if subjunctive concessive clauses can concede facts, might the usage of the subjunctive mood still convey some amount of actual or rhetorical hesitancy on the part of the speaker? In other words, just as we in English say, "That may be the case, but..." to concede something as a fact (but in a non-emphatic way), might the Latin subjunctive concessive clause be employed in a similar manner?