Right now, the bounding box only shows a mild warning that the text element should be kept within lines. Is it possible to not allow the element to move past those bounding box lines at all?
Well, there is always the cropping option, that will simply cut away everything that is outside the bounding box. If this is not what you are looking for, please make a new entry in the feature request forum describing exactly what it is you are looking for. Thank you.