Yeah, I can see this and I am hoping that there will be a way to "crosspost" the same instance to different communities, but I do not think crossposting for twice the rewards will benefit the author long-term - as any autos and support one gets might drop away very fast.
There is game theory in every step of the process here and, it is highly dynamic. Makes it hard to really know what is the best course of action as one has to consider the reactions of a decentralized community, all with their own incentives and agendas. I like it :)