Learn Italian: Il fatto che la diceria è falsa è innegabile. - The fact that the rumor is false is undeniable.

In Italian, il fatto che takes the indicative when it introduces an objective, concrete reality. Because the sentence explicitly states this fact è innegabile (is undeniable), the clause is treated as an absolute truth rather than a subjective opinion, doubt, or emotional reaction.

How would this sentence change if it were expressing a subjective evaluation instead?

If the main clause expressed a personal reaction, you would need the subjunctive. For example, if you said È un peccato il fatto che la diceria sia falsa (It is a shame that the rumor is false), you must use sia. The emotion or judgment makes the evaluation subjective.

Is it strictly necessary to include il fatto in this sentence?

You could technically just start with Che and say Che la diceria è falsa è innegabile, but this sounds quite clunky and highly formal. Using il fatto che is the most natural way in everyday Italian to turn a whole clause into the subject of your main verb.

What is the difference between diceria and voce when talking about rumors?