I've always enjoyed reading these speculation threads from others for books I've already finished, so here's my observations and speculation having now listened up through Chapter 30 in TLM. I am just about to go for a walk and pick up with Sterris back in Elendell doing politics. Spoilers for all other Cosmere novels, and apologies for any factual errors - I'm avoiding the Coppermind like the plague so am doing everything from memory, and sorry for spelling errors - I only listen to the dulcet tones of Michael Kramer.

Please don't confirm or deny anything, just enjoy how right/wrong I am =).

• Moonlight has to be one of Shallan's Lightweavers, right? The specific description of the odd shape to the eyes (Rosharan) as well as an affinity for deception and a mention of not being a Kandra but having other ways to disguise themselves. Definitely keeping an eye out for mentions of odd shapes/patterns around them for potential indications of a Cryptic being nearby. Only other idea is that they're the Herald that is constantly destroying depictions of themselves, given the art discussion (Shalash?). This would indicate that the Ghost Bloods finally figured out how to get Invested individuals off-world sometime during/after SA5.
• Speaking of the way Bilming is being laid out - it sounds very Sel-ish, as if the entire city is being set up to be a giant Aon.
• The Hoid/Ghostbloods interactions, brief as they are, have been great. Hoid losing musical instruments is becoming a pattern :D.
• Melaan going offworld makes me very excited to keep an eye out for her later. Perhaps she's the Kandra we've already "met" offworld?
• At this point the clues seem to me to be pointing to "The Lost Metal" being either Atium, Lerasium, or both. That's a bit on the noise for Sanderson, but who knows.
• I'm verrry suspicious of that secondary explosion in the lab after the initial attempt to split Harmonium. Wax's illness and occasionally seeing allomantic lines absolutely has to be connected. I'm hoping that the split actually did happen and that he ended up getting dosed with Lerasium and this illness is his snapping into a Mistborn. Although I generally like Era 2 better than Era 1 for its story and setting, the lack of Mistborn and full Feruchemists is my largest complaint.
  
• If the split didn't happen, did he accidentally get "spiked" somehow? I don't recall if a hemalurgical spike can be re-used in someone else - if the Trellium spike was hemalurgical and not just for anchoring more than 3 "regular" spikes against Harmony's interference, then perhaps he got Trellium shrapnel and is picking up whatever that spike was invested with?
• The Batman references with Wayne, intentional or not, are pure joy. "Master Wayne." Being filthy rich. Largely not using guns.
  
• Also, Wayne is gonna end up a Bendalloy savant, isn't he?
  
• Loving seeing Marsh really flexing his stuff in broad daylight, and hope they can get him the Atium he needs.
  
• Who is the third person from the first era??? Kelsier, Marsh, and ...? Not counting Sazed, right? Is Spook not actually dead??

I think that's it! Onward!