And using the pedal to cover up non-legato playing, especially in Bach or Mozart, is a real no-no. Later on, composers like Liszt and Debussy would expect you to use the pedal to create a legato effect where it's impossible to do it with the fingers alone. But certainly not in the 18th century!
Nevertheless, in all the music of his and Mozart's that I have played, I cannot bring to mind a single "impossible" legato
However the sequel to that comercial which I found even more magical, featured the D Major prelude, No.5 of the WTC, played legatissimo with pedal. This is the way I prefer to play it now but I can't decide if I am doing Bach a dis-service as such. I find the original staccatto interpretation frigid and uninteresting and yet I keep reminding myself that that is the way he wanted it!
1. maintain an honest fracture in the legato because the human hand has natural limitations; 2. do whatever you physically can to adhere to the composer's instructions (which exist IN THE MUSIC, not in the digitation put there perhaps a century later by some musicologist); 3. blur the entire register of the piano by using the sustain pedal - the pedal is the ugliest and the most cheaty. Even given the lightest touch its indiscriminate smoke affects every corner. I'd even put it on a par with selecting the "strings" sound effect when you are playing Schumann on an electric keyboard. It is rude.
lostinidlewonder, you make good points but I disagree that there is only one best fingering for Bach. Fingering is affected by a lot of different things, the size of your hand, the tempo, the articulation, even which voice you want to bring out. All are variable in Bach.