What people will do first is post their full post to multiple communities...
How is that possible? As far as I know we are only allowed to use one community tag as the first tag.
That would actually solve the problem of publishing the same content (cross-posting) multiple times.
Just copy paste the whole post and post it again to a new community. Cross-posts are more visual than that other method.
You are suggesting to post the same content multiple times? :)
If I remember correctly up until now all the copy pasted posts (copies of older posts, or posted few times) were considered abuse and reported. Those accounts were then downvoted and put in blacklists for spam/reward abuse.