Well, I'm glad that the information is confirmed and that I could help to solve a problem. Now, we are sure that Mugellini has an editited the work.
I think you have noticed that I also uploaded a reprint from Muzyka for the Book I, BWV 846-869. I think this is one :http://www.ruslania.com/entity-6/contex ... 53948.html
The Musyka and PWM files don't come from the same website. Both websites claim that the editor is Bruno Mugellini. Am I allowed to give you the links ? They contain a lots of sheet music, which may interest IMSLP, though some of the sheet are not public domain in Canada.
I'm quite sure for the book one : both are made by Mugellini. You can see the same tempos, fingering, articulation. I don't understand Russian, neither Polish, but I'm sure the comments are the same.
I have some doubts about Book II, BWV 870-893.
The website which contain the PWM, offers for the Book 2 the file which I have uploaded. I have encountered this very same file is on several websites. So I think it is good. There is no title page. As in Book I, there are some footnotes. However, if you compare with book I, there are some differences. The footnotes are translated in several languages : russian, english, italian, french. No polish comments. Is this PWM ? I don't know.
I have not posted the edition "Musyka", though it looks very much like the Book I. A title page is included, in russian, with Mugellini's name on it (I can't read russian, but I have compared the cyrrilic letters with Book 1, they definitely are the same). The titles for each piece "Prelude" and "Fugue" are written in russian. But there are no footnotes. Some indications of tempo, but very different from PWM.
For instance, Prelude no 1 in C major, BWV 870 :
Muzyka says : Andante espressivo. The duration of a crotchet is 54.
PWM says : Moderato. The duration of a crotchet is 72.
I can upload the Muzyka file on rapidshare if you want to have a look at it. But I'm quite sure that tone of the files is not edited by Mugellini.
Again, thank you very much for your time and help. And thanks to Robert Allen.