The post doesn't discuss how they are going to get exchanges to run their closed-source hard fork. It does say (auto-translated):
There are people who talk about the possibility of separating the hard fork chain.
Currently, the main Witnesses are expected to go to 23.0 under agreement. The code is also shared by contacting the exchange. If there are witnesses who do not update to 23.0, they will create a chain that is forked to version 22.0 among themselves. Of course, there is no change to apply to 23.0 in the chain. Theoretically, if there are enough Witnesses running 22.0 code, it's not without Steam's possibility to split the chain
Even if all witnesses move to the hardfork, that doesn't mean exchanges will. Exchanges could potentially face liability for supporting code that seizes user assets. This hardfork is so far outside of the established norms for an open blockchain, that I suspect many exchanges will want nothing to do with it. If that's the case, the hardforkers will essentially create a new token with no exchange listings and very little value.
I'm interested to see how this plays out.