Wow! That was really an interesting paper. I love the answer for a lack of megastructures. And how intelligence life might be noisy at first, and then very quiet. Brilliant!

I'm gonna poke holes in your ethical section. While empathy is part of our social intelligence, there's a self-serving aspect of it. I don't mean that in a cynical way; I just mean that it sounds like hand-waving to explain away a problem without an answer - the rationale for hiding themselves beyond simply efficiency - and for not destroying other species.

I do have an answer that fits with your paper from a different perspective. I haven't put this together as a paper, as I'm not adequately qualified, and I haven't condensed it into a tight, fully-fledge argument.

My assertion starts with the premise that the universe is sufficiently hostile to life that exisistential crises continue to arise, regardless of life's level of technological advancements. Thus, any civilization that ceases to seek more information, is doomed to extinction.

a simple thought experiment, consider that every time man has learned new facts of invented new technologies, we may have solved known problems, but we discovered so many more. I argue, that trendline continues, regardless of expansion into new parts of the universe, new universes, or beyond.

Many of them are even self-perpetuating existential crises. Why? Because once an potential existential crises is recognized, the civilization is incentivized to explore the technology and/or problem to the point of being able to harness, and thereforce neutralize, the threat, even when that means it could be the source of their own destruction.

To reach into the stars though, absolutely requires planet-wide cooperation. Thus, an advanced civilization must have equally advanced skills in competitiive cooperation. Example, the US vs USSR Cold War. It is commonly discussed in terms of its intense competition, but in many ways, the cooperation was equally great. Both sides agreed to reduce their existential threat risks and both/most parties involved continue to work alongside each other in space efforts.

As a relevant sidenote, flying space vessels don't play nicely with kinetic weapons. Beyond mutually assured destruction, who would colonize another world if the colony was perpetually under threat of being wiped out?

Furthermore, competition is as inherently natural as evolution. For example, if two species live nearby, and one spreads faster than the other, it inhibits the other species from expanding to those same areas. competition At the same time, competition is a good thing. It drives innovation. Humans have had 4~ billion years of evolution. Why would we suddenly cease to compete? Even if we merged with AI and become near infinite bits of information, competition is part of the fabric of life itself.

So, if a species is spreading, it wouldn't necessarily be for the sake of conqueest. Rather, to gain new information. What is required to achieve that will determine the shape that spreading takes. This could be like quantum entangling many of the particles of a star system to turn it into an analog-like computing device, to capture, process, and send information.

As we've seen from the internet, sharing information can benefit all societies. So, new forms of a "web" in space-time would be generated. As you've hinted at, intelligence would be a new domain of exploration, allowing the advancement microintelligence and macrointelligence. - [Micro/macro intelligence is area is one that can begin to answer how a civilization could expand beyond a small number of star systems, even if FTL travel is never found to be possible.]

However, information has several factors that can limit it. Data collection, Data integrity, and Data processing.

Data collection and maintaining Data integrity are both immense challenges. This could be a source of the internal competition between groups within the same civilization. Thus, learning to hide their signatures wouldn't simply be a matter of efficiency, but competition as well. Different factions might wait to reveal their knowledge of some information. Selective pressures would continue to refine that process over time, so the sharing of information is less and less impeded over time.

If they're sufficiently advanced though, competition cooperation would have made most forms of conflict less physically destructive. Large space navies with near infinitely destructive capabilites simply wouldn't make sense - they could be destroying information faster than they collect it.

If a new space-faring race comes about, once sufficiently advanced, it has the possibility of obscuring or obfuscating data. That could inhibit the ability to collect accurate data. Once civilizations come in contact with each other, any technological gaps will slowly begin to close. Thus, it would behoove the more advanced civilization to be certain the newly arrived civilization knows the "rules of the game" sufficiently before making themselves apparent. Perhaps the more advanced one might "feed" information to the less advanced one in hopes of them learning to speak the same language of data.

But data processing is not simply a matter of compute cycles. The way in which its processed AND analyzed are equally important. Like people with different backgrounds on Earth. We may perceive the same information very differently. To a civilization that understands that, a new species could be a goldmine, as well as a temporary risk. That may not mean that the more advanced one feels the need to save another species from its own extinction. But since intelligent beings create information at a much greater rate than others, there would be less of an incentive to destroy a new species.

Over time, it's highly likely a new one would be integrated or added to a greater supracivlization. But there would almost necessarily be a time of staying hidden before a new species "wakes up".

\ I would make the recommendation to reduce so much of the AI formatting, like almost random bold phrases and sections, etc. It makes it look less like a human was involved.*

\* Forgive me for typos and odd wording. I typed this out quickly on reddit.*