If a new student to French wanted to compare their levels to those of these people, at what level can their literacy be measured?
For example Jean could not read or write (correct?) so would this mean a beginner to the French language would already surpass her intellect after a few academic semesters? If she was religious, is there any reason why she could not learn through the church.. I mean she would have to read the Bible right?
Did Napoleon simply have an accent or was he obviously not entirely fluent either? Is there any way to know their knowledge/fluency of the French language?
Concerning Joan, no she would not have to be able to read to read the Bible, the local priest would do that for you as the mass.
Do not mix intellect and knowledge. She was probably not knowledgeable at all but would probably be intelligent enough to do what she did. I did not study Joan extensively so I will leave that to someone else.
Napoleon did not speak French at all as a child and learned within a few months after entering "collège" (not the US college with is university, collège in France is just before high school).
He then goes to military school where he is noted as brilliant in mathematics but mediocre in litterature which seems consistant with the fact French was a rather "new" language for him even though he apparently was fluent at that point, probably with an accent though.
The language issue is not mentioned after that in his various biography though so I assume he spoke more or less like a native. I had the chance of reading letters wrote by his own hands (Parma in Italy has a museum consecrated to him with several letters) as an emperor and even though they are wrote in the French of the time they do not seem awkward in any way, maybe he got help but as some of them are love letters he may have been reluctant to get helped on these ones.