Moussorgsky - To Do, or Not To Do?

There is a dilemma which, from time to time, confronts those of us who pursue the profession of music, and no argument is ever lost or won - the issue involved remains.
In this case, it deals with the 're - writing' of a masterpiece by someone other than the composer. I am not relating to the writing of transcriptions of originals, such as the nine symphonies of Beethoven having been reduced to piano in a most masterful way by Liszt - I am, in this case dealing with the problem attendant with "Pictures at an Exhibition," by Modest Moussorgsky.
It is well - known that Moussorgsky, like others during that wonderful period of defining orchestral works in Mother Russia, was lacking in much training as a composer. One must remember that many of these composers, who are now so well-known to us, were composers by avocation; everything from law clerks to artillery officers etc., who wrote music in their spare time. It's still remarkable to me that the likes of a Tchaikowsky, for instance, whose music is world renown today, was not a composer by profession, initially.
And so it was for Moussorgsky, whose ideas in composition far exceeded, in sheer musical genius, his abilities, periodically, to commit them to paper.
As an example, if one looks at his "Pictures," one will find, in the manuscript, several errors in notating, even rhythms.
And so the likes of Horowitz actually 'enhances' some sections of "Pictures," often by addition of notes, to project greater power of the genius of Moussorgsky. He would be the first to state that the composer simply did not have the writing technique to efficiently project his wonderful concepts over to the piano. And Horowitz stated that opinion more than once, I assure you.
In the recordings of Horowitz's "Pictures" one will hear the greater power of the message through his own 're-writing,' and these incarnations are thrilling examples of pianistic portrayals of the composer's undeniably great ideas - be reminded that Horowitz does not alter the germ of the music; that is, the themes - that would be crawling into the bedroom of the composer's mind; obviously not an acceptable process to any of us in the field.
Andsnes also embellishes, in his recording of "Pictures," to further strengthen, in his opinion, the wonderful material that Moussorgsky gives to us. He uses the term "dirty notes" when discussing the masterful way that Horowitz adds to the original work in a way that these additional notes are veritably "invisible" - Andsnes adds that this is the genius of Horowitz in his pianistic 'orchestration' of "Pictures."
And so, the dilemma exists. Purists will say that this process is artistically 'immoral.'
And there are those who support a Horowitz or an Andsnes, in their quests to give more power of projection to the music.
And whose side are you on?