When someone goes to a plus card +*right, Wagn acts like it's a set card it can deal with, letting people create setting cards, etc.
Similarly, any plus card +*right +[any setting] acts like it will work and should instead give a message explaining what's wrong.
Give a message something like:
foo+bar+*right is not valid set card, because foo+bar is a plus card and the right side of plus cards must be a simple (one-name) card.
Did you mean foo bar+*right?
give error message for plus cards plus *right+discussed in support tickets
give error message for plus cards plus *right+relevant user stories