Got it, thanks for clarifying.
I'm not sure that I would prefer a single pixel to a cross shape, since pixels have got vanishingly small lately, and this trend might well continue. A cross shape is a bit ugly but has the virtue that it can be seen (at least, much better).
But when presentation is more important than analysis, I really would like to be able to turn the placeholders off completely. As long as the option is applied after initial rendering--so that, if I give all areas a very fat boundary, or make lines very thick, I want to see the object rendered, even if it would be smaller than one pixel if rendered with a thin boundary (or none). (This is a useful habit in Manifold 8, to make all areas and lines visible no matter how tiny. Good for detecting errors not seen at usual scales.)
The placeholder option could be per-map, accesible from the View menu, or it could be per-component, incorporated in whatever dialog winds up governing visible zoom ranges (and possibly rendering scales, if that happens as well).
An extra option in that dialog could be "Show line and area placeholders at small scales", i.e. whenever an object is smaller than one pixel, as now. On or off.