Thank you for sharing your experience. Running into trouble in an unfamiliar foreign country is something many of us face the threat up, and we hope our number does not come up.
What I'm about to say will be controversial and unpopular, but I'd say this first bit is where things went south:
We later learned that one guest had a questionable test result prior to boarding. 3 days into the trip, this guest took a self-test, and was Covid positive. The boat operator reported the information to the local authorities. They met the boat at the port upon our return.
You left out a step, between 'this guest took a self-test' and 'the boat operator reported.' The step where 'this guest opened his mouth about it, which put the boat operator in a bind of having to report it, which derailed all the passengers' after-trip travel plans,' leading to:
We were taken to a dirty, poorly maintained facility, where we were detained for 48 hours before going to a government controlled test site. Results of the government tests - 16 of 21 passengers positive and 0 of 27 crew positive. We self-administered rapid tests, which were all negative. We were asymptomatic. They held the positives in this facility for another 6 days. The conditions were deplorable!
There will be a range of opinion on what such a guest should do. I'm fond of the path that doesn't derail everybody else's travel plans in favor of mandated confinement. You could wait till you're off the boat, notify your airline of your situation, and handle things privately. Other option is don't test yourself till you get home and maintain full deniability (you could wear a mask and try to social distance).
In fairness, if other people have, or are around, people with sniffles, sore throat, etc..., as easy as test kits are to get in a number of places, seems if they were really curious, they could test themselves privately.
Some people can make an argument for testing and notifying. The counter argument would be SARS-CoV-2 is so widespread that people are exposed intermittently anyway, and maybe it's time to accept that. Which some people will hotly deny.
I bring these things up not trying to change minds, but because increasingly as we go forward in dive tourism, these situations will arise.
3. Puerto Princesa is a tiny provincial town and the quarantine facility is probably set up for the local. Therefore foreign tourists might find it unacceptable.
Thanks for the notice it's a small place that might not be representative of the Philippines as a whole (or at least parts of them).
I am surprised at the sentiment the Philippines is a '3rd world' nation where divers shouldn't expect what Americans might consider reasonable basics (I'd say running water, A.C. or at least a good fan, electrical outlets, strong preference for western style toilet with toilet paper, at least fair wifi service).
Our hobby encourages people to travel and directly experience places and peoples and I'd rather it didn't come to American divers thinking only places like Grand Cayman are suitable. If someone is going to a home stay, okay, they hopefully know what they're getting into.
Given that SARS-CoV-2 seems endemic worldwide (we could argue on China), cases are common, and liveaboards combine sizable groups in close quarters for extended periods after traveling crowded airports and planes from abroad, if all it takes is one person deciding to test for cold-type symptoms
and announcing a positive result to derail everybody's trip, that's a problem. And no, travel insurance is not a cure-all.