Comment by TeMPOraL

The way I interpreted it is that Scissors just are. For a given group, at any given point in time there are maximally controversial statements, "edge cases" that can collapse communities. They are not obvious to anyone involved, and they may change over time.

(Imagine this as fuzzying communities. Crafting inputs that trigger worst performance of an algorithm, hit a point of numerical instability, or straight out exploit it as a security vulnerability.)

In the example of wedding cake, at some point in time, for a large group of people one of such "maximally controversial statements" was a statement about a bakery refusing to make a cake for a gay couple. The US is large, so things like this just happen. And one of such cases happened at this particular point in time where statements about it are Scissors, people started talking about it to each other, and the whole thing exploded into a national scandal.

What I believe the protagonist of the story had is a Scissor predicting machine. A social fuzzer. The difference between using it and waiting for a Scissor to be generated organically is that the event need not actually happen. All that matters is that a controversial idea is posted.

Think about it for a moment. Did that story with bakery really happened? If you're only causally made aware of it through social media, would you be able to tell if it was just a fabricated story spread by a bunch of folks on Twitter? Do you think people involved in the drama on both sides of the issue actually verified it? (And no, mainstream news outlets aren't good at checking their sources either.). The point of a Scissor is that after a while, it doesn't really matter what the statement is about, it's simply a catalyst of group division.

In the real world, I would hope a Scissor based off fake news would have less impact than one that grew organically out of a real story. Within the story world, I think Scott Alexander makes the point that a computer-generated Scissor is just as much if not more effective.

So, to answer your questions: the Russian Scissor Machine generates a statement about a bakery refusing to make cake for a gay couple. They post it on-line on US social media. People start getting at each other's throats. Maybe it so happened that there was a bakery that at roughly that time refused to make a cake for a gay couple. If so, someone finds it and it becomes the object of the Scissor statement. If not, no big deal, someone in their zeal fabricates a story, and it's not like either side actually has time to verify facts between retweeting and downvoting. At no point anyone is paid or bribed or otherwise aware of what's going on. The Russians just post a statement and watch the US people tear each other apart.