JJ Abrams already confirmed that Kylo Ren wasn't a Sith. In a pre-release interview he said that he wasn't a Sith, and that he was part of another group called the Knights of Ren. Presumably that's the case for Snoke as well, since we know he's a force sensitive.
I'm also guessing that is why he carries a slightly different weapon than the Sith.
I acknowledged that Kylo Ren wasn't a Sith. I edited my post from Sith to Dark Side user. I know of the Knights of Ren, though it sounds like the Knights of Ren are more like the Emperor's Hands(Kylo is the only one in the flashback shown to have a lightsaber). As for Snoke, he can go either way since we don't know much bout him.
What different weapon? The lightsaber may be a unique design, but that isn't unheard of, especially in the EU. Even in the movies, Darth Maul is the only person to have a dual-bladed lightsaber so is of unique design.
That's because they knew him before he became Emperor. Once he became Emperor, there was no need to call him Darth anymore. And plus it's a respect thing. You wouldn't call the president senator, would you?
I know. What I'm saying is that like Palatine who dropped his Darth persona when he became Emperor of the Galactic Empire, Snoke could of dropped his Darth persona when he became Supreme Leader of the First Order.