> Discord’s action is effectively market manipulation in a literal sense, because this is certainly going to affect the market.

It certainly will have an effect, but I'm not sure it meets the definition of "manipulation". I think (though am not certain) that the manipulating party would need to have a stake in the market asset for manipulation to apply. Many definitions (though not investor.gov) imply that personal gain is a requirement. No doubt there will be a legal case made here.