No idea where they’re intended to go, but honestly those ‘sith whispers’ are very out of place during that moment really pulls you out of the climatic moment with Rey and Palpatine.
If it’s strictly Palpatine vs. Rey, then yeah I agree. I’m working on emphasizing the “I am all the Sith” idea throughout the movie, with Palpatine’s current body literally containing the spirits of the Sith that came before him. If this is included, it wouldn’t come out of nowhere, it would be built up throughout the movie whenever Palpatine speaks.