Oof. This sucks, I'm hoping this was just a random Wiki editor with some kind of grudge against Fessler because that would suck as an official obituary or position of historians and philosophers.
Ignaz Aurelius Feßler
"Fessler was a voluminous writer, and during his life exercised great influence; but, with the possible exception of the history of Hungary, none of his books has any value now."