The great bulk (if not all) of PPC History works are his, so if anybody knows what's up with the Civil War, it's him.

That said, as to "how we know about its existence," the ex-universe truth is that somebody somewhere thought it sounded like a cool idea and may or may not have had plans to write about it. That doesn't mean you personally have to subscribe to it. So, I guess my point is: don't worry about it too much. Unless you want to. {= )

~Neshomeh

I have nothing helpful to add; I'm just going to throw some punctuation at you.

As far as I can tell, the PPC's civil war doesn't have any work done on it yet. It could be a project for someone who wants to write about PPC history, or could have been already claimed by someone. If anyone knows more about it, please do post here; I'm curious, too.

The only thing I can find that actually covers this time period is "Origins"; and it doesn't mention the civil war:
Origins

I think I will do what I do best: Engage in rampant speculation.

We know that the Civil War happened about ten years before the Cascade (the expansion of HQ) and before the destruction of Origin.

Significant facts that may play into the civil war:

--"A Trekkie's Tale", and the Mary Sue concept, was written in 1973; and fan fiction was becoming much more popular as fanzines were published. At this point, World One became widely aware of the Mary Sue problem. The workload would have increased for PPC agents, who at that point may or may not still have been primarily Flowers.

--At the time Makes-Things dropped into the PPC, the Flowers were still routinely blowing up worlds that harbored Mary Sues and their attendant wild plot holes. We also know that, at some point, they stopped doing this; and that today, killing a canon character is grounds for decommissioning.

With the increased workload, the PPC must have tried to kill more Sues, faster, somehow. Chances are, more and more planets were simply destroyed. But at the same time, with World One having found out about Mary Sues, an increasing number of human agents would have been dropping through plot holes and into HQ. The human agents can't have been happy about the destructive nature of the PPC's shortcuts to 'Sue destruction.

The result was an organization with two groups of people who had different goals: The Flowers, protecting their own existence; and the agents, protecting the continua they loved. How Origin and its residents factored in is unknown; it's likely that the Sunflower Official, probably along with some of the other Flowers at HQ, was also against the destruction of worlds. With Makes-Things's new technology making it possible (but risky) not to destroy worlds, the SO must have tried to change things. That would have created serious tension between the SO and anyone who didn't want to protect the continua--quite likely including mostly those who hadn't ever seen them, i.e., the residents of Origin.

Just blowing things up was an easy option, of course; but it weakened the continuum even as it prevented plot holes from spreading. But surgically removing the Mary Sue is risky because the escape of a Sue into HQ could theoretically spell the doom of all of existence. The question, "Do we destroy worlds, and save ourselves? Or do we risk everything to save the continua?" may well have contributed to a civil war; though like most civil wars, it's highly unlikely that that was the only issue facing the PPC at that point.