Hope this doesn't come off as too "advertisement"-y for my stuff. Alas.

I don't think it does at all. I think it's clear you're providing the content for those who want it, while acknowledging that not everyone would appreciate having it placed in front of their eyes without warning.

I've continued to advance some of my speculation, continuing off of the recent addition. It does pull a bit on leaked materials, so if you dislike looking into that stuff, don't read on ahead. I won't put the text here, and instead link for safety. I'll be expanding it in the days ahead. Hope this doesn't come off as too "advertisement"-y for my stuff. Alas.

Destiny Speculation

Some really good speculation in there!

I just want to add that if the second text is about Mars becoming habitable, it would be because of terraforming not a natural cycle or what have you. Especially if this is about someone analyzing humanity.

Why do I think this?

"Your voice flows across the red rock
and through the dead valleys, speaking in code
and goads."

I take that to mean that the terraformers (humanity) are guiding the process (goading), probably through some sort of mechanical means (code).

Also...

"Every moment matters. And from a great
distance, in the midst of a thousand careful
disasters, you watch the transformation
with your own eyes."

"Careful disasters" speak of engineering, ergo me thinking it's been purposefully terraformed. And watching these unfold from "a great distance" makes me think of a ship in space guiding multiple processes down on the Martian surface.

Cool stuff.

Warning: discussion of leaked content follows

Like you, ExigentContact, I also think these messages are from the perspective of the Traveler. I also think that they are related to their corresponding planet, but not necessarily about the planet itself (for example, Day 1 seems to be more about humanity than the moon).

Day 1:
The best voices--voices that truly matter--never
allow themselves be heard. This lesson is worth
learning again and again.

Forever.

Your voice moves as whispers, murmurs and urges
inside larger winds. Only the trusted few can absorb
what is necessary. Wise and sly and perfect, your
instructions drop, leaving nothing but the hard sweet
rime of enlightenment.

The path is set. Your voice is unleashed. Except now
it is gone...

And maybe it never was.

I believe the first two paragraphs are the Traveler's introduction, and it tells us a few things about the Traveler. It is very old, very knowledgeable, and does not communicate.

We learn that humans were just one of many species in the galaxy, and a rather insignificant species at that. Then, either through our own efforts or through a discovery, humanity became a spacefaring race... and was then nearly exterminated.

These are all ideas that the leaked content seems to support.

Day 2:
Life waits inside this world's bones.

Your voice flows across the red rock
and through the dead valleys, speaking in code
and goads.

Ancient volcanoes swell, exploding at their
peaks and splitting wide along their
shoulders. Ash clouds blacken the starved
air. A fossil ocean of ice softens and
collapses; geysers erupt, tall as mountains,
throwing up steam and clouds.

Every moment matters. And from a great
distance, in the midst of a thousand careful
disasters, you watch the transformation
with your own eyes.

The rose has blossomed.

I think this is pretty straight-forward: At some point, we terraformed Mars. What I find interesting about this is that it is written in present tense. If, as the leaked content suggests, there is only one human city left--then there's no way we could currently be terraforming Mars. Either the tense of these messages are irrelevant, or the Traveler has been watching us for a long time.

Day 3:
One face is blistered, the other plunged into
a brutal chill. Is this how it's always been?

You remember hot oceans, nourishing
atmosphere. But something transpired,
kicked what was wet and fertile into space,
stealing away everything of value. Or
perhaps what thrived here for a day or for
ten million years decided to leave, peeling
its wet organics off the bones.

A name offers itself, and another, and a
thousand more.

The answer feels like the iron heart of a
collapsed star, and you realize the union
between the past and the future is now.

There's no reason not to expect this to apply to Mercury. At some point, Mercury supported life--perhaps not human life, though. I'm getting a Reaper vibe--that whatever is attacking humanity has attacked many species (names), and that the union of the past and future is the realization that the cycle is happening again--another species is being exterminated. The iron heart of a collapsed star could refer to a black hole--a truth that cannot be escaped.

Thanks for pointing this out. I didn't even notice the change, though we did include that in today's posts. I'm updating yesterday's summary now.

I'm not really up to date with all the speculations, but perhaps it's possible this is talking about Earth? We remember oceans and the like, but then something left and they disappeared. Maybe the Earth became tidally locked to the sun in the process, and whoever wrote the text is wondering if it was always like that.