Out of the harpsichordists I've listened to on YouTube, the one that made the biggest impression on me was Trevor Pinnock. I like his approach in general, and in particular, I liked the way he played
the gigue in the e minor partita. For those that are unfamiliar with that gigue, here is
a performance by Pletnev, essentially the way it is written by Bach. What Pinnock did is particularly interesting to me because of the gavotte that precedes the gigue. It is written as if it were 3 against 4, with dotted-eight/sixteen groups in one hand and triplets in the other, but performance practice was to align the sixteenths with the last note of the triplet. In cases where there are two sixteenths and an eighth, one approach is to play them like a slide, and the another approach is to play the group as if it were a triplet. It is the 3 against 4 that dictates the performance practice considerations, but though that problem is missing in the gigue, Pinnock applied the same approach to the gigue that most people apply to the gavotte.
For ornamentation, I enjoyed listening to Andreas Staier. Here is his interpretation of the
c minor rondeau and capriccio
Similar to the way Pinnock played the e minor gigue is
Schiff's interpretation of the c minor corrente, on the repeats (the first time through, he plays it as written). Staier does something similar-ish with the corrente, and so do some other harpsichordists that I listened to, but I think that Schiff's interpretation is the most convincing. I guess this sort of thing is what I'm talking about when I say I'm trying to find out what is acceptable, and what is not.