Seems a bit bullshit from an artists perspective. If I am putting on some works and looking for an audience, or want to share digital works, I usually post to multiple groups/pages, for example, on Facebook.
The inability to crosspost, or share posts to different communities make them seem, like they are going to be about milking upvotes, and whichever communities has the most upvotes, will become stronger and attract more people due to the votes, and inevitably become the reigning community, due to voting power alone, and not community.
Hopefully more functionality will be added, like how you can rebog your posts from communities onto your blog, perhaps we will be able to repost the same post onto communities without having to resort to multiple of the same posts.