I'd probably snag all of my neighbors' generators, maintain my dad's house and live happily by myself. He has a farm, so I'd be using it to survive.
I also most likely wouldn't guess that blockland forumers would be the ones to have survived, so I'd never really go looking.
Before the internet starts to become dysfunctional (which would likely happen pretty quickly) I'd save hard copies of as much important scientific and mathematical information as I could. I would pirate all the music, maybe tracking down Spotify or Apple's servers.
I'd also locate the houses of some of my favorite musicians, and take their instruments and recordings.
I'd take medicine from the nearest RiteAid.
I'd probably also take my neighbors' guns and learn to use them, but I might just end up using a bow and arrow since finding ammunition would likely be a chore and I have more experience with a bow.
After all this, I might start moving around somewhat regularly. I'd use a bicycle, since gasoline wouldn't be a hugely accessible resource. I'd raid the solar electric shop in the nearest city, and see if I could install solar panels on my roof. I'd figure out how to broadcast radio and perhaps go to NYC or Boston to see if anyone was there. I can handle being alone, but I don't think I'd want to be alone forever.
I'd mostly be doing it to make sure that people don't starve. They could work at my farm and things would be generally okay.
When I did start finding people, we'd eventually figure out that blockland was the common thread between us, and then we'd probably try to access the blockland forums to check the topics where forumers have given their location. However, at that point, it most likely would already be down. At this point, the only way of finding out would be to somehow track down the location of cloudflare's servers, since blf use cloudflare. There is a list of locations available on their website, but I don't think it would be up either.
While the ISS might still be streaming video of Earth to Earth, I doubt that it would be particularly useful. Unless somebody thought it was important to use a whole lot of light, it wouldn't be all that useful to make the trip to Washington DC to visit NASA's headquarters and see if I could possibly access that data. Still, I'd probably try it a few years in.
For heat, I'm lucky that my dad installed a radiant heating system in our floors, and a wood burning furnace to heat the water for it. I could probably gather enough wood to feed it through a winter and keep myself pretty decently warm.
We have a well on our property, so I wouldn't run out of water, it's just the aforementioned electricity that would be an issue.
Once I'd found other people, I'd actually be pretty well situated to accommodate them with my dad's house. We have 10 beds in all, and we could still easily house about twice that many people with a minimum of discomfort. The issue would be feeding everyone, and that could be accomplished by having everyone help out with the farm, and perhaps hunting as well.
The main issue would probably be electricity, but there are still plenty of generators around in my neighborhood, and while they might be ones that use gasoline, if we put our heads together we might be able to take one apart and put it back together in such a way as to be able to generate power using fire.
After all this, there really wouldn't be that much left to do other than live in relative comfort. If people wanted to build or use other houses, they could move out, but I would happily house whoever remained. Humanity wouldn't likely survive, but it's technically possible. It might depend on whether lurkers and inactive/banned members are included.
Technology generally wouldn't regress entirely, but medicine would be sorely set back. The life expectancy among the survivors would likely be something like 35 or 40. A large amount of the reason why people died so much younger was simply poor hygiene, and while forumers are probably not the most hygienic bunch, we're still a lot better off than people used to be.
The remaining population would be pretty young. A bunch of the super young forumers would likely just die out, but the average age would likely be somewhere around 16. Authority figures would most likely just be the most charismatic or well-situated people.
Since forumers are mostly situated in the US and a bunch in Europe, those who remained in other continents would have a worse chance of survival and the remaining people would still certainly all be English-speaking. If the human race survived, it would be everyone's first language, and since communication would still often be internet-based after the internet eventually went back up, there would be no reason for the development of new languages. However, there still could be separate cultures.
For the first time in a long time, the human race would be once again subject in a major way to natural selection. While there would be a small gene pool, it would likely be that of the strongest and most social of us. Inbreeding might end up as an important concern. There would certainly be enough males, but there would not be a lot of females.
Survivors would end up in villages. While many of you say that you would live alone forever, you most likely wouldn't. In all likelihood you would either find others or you would die.
People crossing the Atlantic or the Pacific are both pretty unlikely.
Those who remain in South America might make their way up, but it could be pretty tough.
People living in the city would likely end up having to move outward to find or grow food after several years of surviving on the remaining good food raided from supermarket refrigerators.
The barter system would probably be the norm again, since currency wouldn't really have any meaning and people could easily get wildly different amounts of money. Eventually one would probably emerge, though.
