So... good morning all, and welcome back to me, who hasn't been on this forum for a while now!
I cannot believe such a fine bunch of musicians as yourselves have managed to speak on articulation to this extent, without mentioning acoustics.
Allow me to generalise, and say that Bach himself performed mostly in very large acoustics, whether at court, or in churches. Modern concerthalls fall usually within certain parameters - optimized mainly to romantic symphonic repertoire, piano recitals, and sometimes for clarity of the spoken word. Now obviously if one were to record a piano disc [Liszt, Rachmaninov, any of the big stuff], somewhere like the Boston Symphony Hall might be your preference, if you could get it. And most modern concert halls are designed to fall somewhere in the vicinity of this room.
Now back to Bach... and if you look at the places he performed his music, on a weekly basis, you see that they are generally far more cathedralesque... sounds are more "floaty" and less direct than the most acoustically-generous of modern halls, not to mention far longer reverberation times [perhaps 8 or 9 seconds compared to about 2 in Boston Symphony Hall], and "wetter" or at least "less clean" sounding.
If you hear perhaps a Bach Cantata in a European cathedral/church, it would probably be a far different experience to the same cantata sung by the same choir, in a modern concert venue.
So, by extrapolation, I would propose that, as a rule for a good musician, the playing must be tailored to the acoustic. The same prelude and fugue would be played very differently in [1] Notre Dame, [2] Boston Symphony Hall, [3] a lounge room. In all three cases, the instrument could well be the same [a Steinway B, a harpsichord, whatever], but the playing would change.
In the same way that Bach on a Steinway is far from "original practice", so too is Bach in a modern venue. Now what I don't understand is why today's pianists, performing on Steinways in modern halls, are so interested in authenticity.... "Bach didn't play legato, so I won't".
I'd say Bach was a musician first and foremost, and tried to get the best and most musical result, using whatever was available.
However, to be scientific about this, my main point is that "articulation" is really an acoustical question, if one is interested in the "effect" of the articulation moreso than the "cause" [the finger's duration and touch on the key].
So surely this is the startpoint for a musicians' dialogue on Bachian articulation?