It probably would be a more effective campaign for subreddits to have their users wipe all their old comments (older than 1 year) than a temporary blackout for a few days.
It's the right of each user to redact their contributions. If that's the only bargaining tool then it seems entirely reasonable to use it when the other party refuses to negotiate or even be remotely transparent about their motives. If this was really about money then why do we have such little insight into their financials? Could it be that they fleeced the investors and will lie as hard as they can to not be outed for the crooks that they are? It's the most likely explanation from my perspective.
There's no reason to prop them up. The information will be rebuilt quickly or it won't.
People didn't post on Reddit for Reddit, people posted on Reddit in the hope that other people might read the post and get something out of it. Burning all of the books that I wrote for others to read is attacking myself to hurt Reddit. I don't care about Reddit enough to hurt myself to hurt it.
In that case, the script could be modified to archive all the comments into a local file -- you could restore all your books back to the library (Reddit) if you chose, once they stopped threatening customers with higher fees.
If people were really committed, they could "unionize" and have a centralized party which held access to their comments, but that would probably violate their ToS and would not set a good precedent for an open and free internet. Not to mention, Reddit could easily just block users from modifying/deleting old comments.
all of the web's useful information--decades of discussion--is stored in reddit's garage. and they've decided to close the door.