Very confusing indeed but I think we can assume that it's like in English, where "speak" needs "of" when you mean you're speaking OF a subject, and maybe italians feel that everything that is spoken of is a "subject" and not just a word.
when i interpret this literally, i get "They say of no". Am i interpreting this wrong, is this just some sort of phrase that means something other than the literal translation and we need to just memorize it?
is di a preposition here or a conjunction or a verb? the hover dictionary indicates it's a verb. Notice too how much clearer the anticlutter message is to read than the pale low contrast lessons. I'm going blind with these fonts and backgrounds.