Sure there is space for plenty of discussion about historically informed performances. What I really don't understand is how pianists (I'm talking about the famous names, not we as learners. =D ) consider, with NO EVIDENCE, that there is no rubato in Baroque music. Evidences point that there are much more rubato than that music from Romantism period. I could cite a whole page about rhythmic irregularities described in lots of Baroque treatises, including that of CPE Bach (there are two pages of it in Roberto Donington's book).
It's just a matter of getting used to it. I myself didn't like this "ligering" of some notes when I first heard it.
We don't know when to use inégalité and when not to use it... You're right that inégalité is more exaggerated in French music. But all of this is very subjective. What seems to us to be exaggerated, possibly is extremely subtle to a Baroque exuberant mentality.
I think we must translate the Baroque intentions to the piano, and not play it like it was a harpsichord. The articulation on a harpsichord is very subtle. There is a main concern for playing very legato, otherwise the harpsichord doesn't resonate. But sometimes I think with the piano we should do exactly the opposite: the articulation should be clearer, because the piano has a huge resonance.
There is space for plenty of discussion, and this is all very healthy. And there is no correct performance also! Mainly in Baroque period, where much liberty was left to the performer, there are several ways to "solve" a piece.
You're right that the articulation is a way for marking the strong beat. Harpsichord doesn't have dynamics. But this piece was also written for clavichord, which does have. I think that not doing this baroque articulation just because it is "not necessary" on piano is not a good solution, because it subtracts style characteristics, instead of adding. Since the piano has dynamics, I think the best solution would be to do both: articulation + dynamic. Afterwall... this articulation affected the rhythm!
There are some rhythmic ways to describe changes in structure which we usually do on piano through dynamic contrast. I think it's more "baroquian" to do both on piano than simply doing the dynamic contrast, which sounds more romantic.
Regarding rubato, Leonhardt plays a chaconne with lots of inégalité. And so does his pupil, Robert Hill.
It has been very difficult to me to study and understand this baroquian agogic. The first time I played inégalité I was so tense that I couldn't breath! I had never played that way before.
That's why I like these studies: it helps me see music in a broader way. XXth performance practices are too restrained and boring... there are so many other ways to play music. I always disliked mechanical Bach approaches, but I didn't have any *excuse* for playing differently. Now I do.