Users sometimes create a banner that includes a single variable. A bunch of single variable banners is going to slow down their document. It would be great if we could prevent them from doing things that will slow down their document by reverting the banner to a question/variable it was crossed by. If we can prevent other behaviors that will slow down the document, that would be fantastic! If we can't stop them from building a banner out of a single variable, we should at least warn them.