Well, one question answered today, at least a little bit. Jesus specifies not to tell anyone until the Son of Man comes back from the dead, which is a pretty decent code as far as codes go. I don't read that as applying to everything, but at least for today, I think the disciples did as they were told regarding keeping secrets.
Today's passage seems to focus more on the divinity of Jesus. We see Jesus meeting with Elijah and Moses, who are two of the more important Jewish prophets, and He's in "God clothing" and gets another shout out from God. Jesus, at least in retrospect, seems to pretty clearly be from God. Peter already knew for sure, but now James and John had to feel pretty certain about something Messianic, right? There's some favor from God, more than we hear from Moses or Elijah. Both of them may have met with God, but Jesus is the only person who gets praised by God.
I don't really understand that last part, though, about how the Son of Man negates Elijah (the word "yet" is particularly confusing). I mean, prophets were told about the Messiah. So unless the Elijah-coming-first part references that Elijah saw everything unfold as it does, and Elijah's coming was actually time traveling paradoxical wibbly-wobby timey-wimey stuff, it doesn't make sense. I mean, it doesn't need to, I guess. Elijah came. Jesus came. Elijah technically came back in this passage. Maybe that is what is meant.
Anyway. Jesus is God. I knew this. Moving on.