Dogen never intended for Sayid to kill Smokey. He was planning for it to happen the other way around.
The only people who said that are Smokey and, parroting Smoky, Sayid. Dogen never denied or acknowledged that it was accurate, which is par of the course for
Lost. Honestly, if Dogen wanted Sayid dead, he wouldn't have to go through such ceremony. Especially considering his last attempt to do so. Or what, you think his plan basically amounted to "Oh hey, Sayid, s'up. I know I banished you and shit after a moment of introspection earlier, but uh, here, take this knife and go stab Smokey for me. It'll totally work, dude, and in no way is he just gonna kill you for trying. I mean, it's not like I couldn't just say a word and the twenty Others nearby would shoot you dead on the spot. No way! So, uh, yeah, go do that for me, would ya? kthxbai. Oh, wait, here. Take this dagger. But wait, see, it's in a magic box hidden in the soil deep in my secret underground lair. That makes it magical (even though it's just an ordinary knife I buried for just such an occasion), so this'll totally work, dude."
Furthermore, there has to be a reason that dagger was special. Dogen had it protected in a special, engraved box and carefully hidden deep inside the temple (in his personal abode) and out of Smokey's reach. Considering also that Dogen was the sole defense against Smokey at the temple, I think that says a lot more than a few words by a master liar and manipulator, aka Smokey. Doubly so since Dogen had no reason at that point to try and kill Sayid in such an obtuse and absurd manner that even a Bond villain would roll their eyes at.
I don't think they made a big deal about Locke not speaking to Kate.
They most certainly did make a big deal out of it. It occurred in the same episode, and not long after, Dogen told Sayid how to kill Smokey. With that attack failing miserably, presumably because Smokey
did talk to Sayid before he did it.
It was more a moment of surprise and intrigue for both of them. Locke was intrigued that Kate was one of the survivors of the Temple, and Kate was shocked to see Locke standing there alive and well.
That was the circumstance of
why he didn't speak to her, but the emphasis of the scene was that he
didn't speak to her.