This morning I started browsing through YouTube to compare a few Beethoven interpretations.
Listening to Richter's Pathetique, I remembered a "gloss" from the Ricordi editions of Casella (a most noble musician, moreover) regarding the mordents of the second theme, which greatly disturbed me when I was a boy attending the conservatory, annihilating my self-esteem and contributing significantly to the failure of my studies, of the following tenor: "if the mordents were not performed on the upbeat... The speed of the tempo would produce this horrible interpretation (followed by the writing in triplets) whose ugliness does not need to be demonstrated to true musicians".
So according to Casella, Richter (just to quote him, among those who perform the mordents on the beat) would not have been, unlike himself, a true musician.
Everyone has a sacrosanct right to think and perform as they wish. However, intolerance should be avoided, both out of respect for others and to avoid making oneself look ridiculous.