Steps to reproduce the bug: Set "Tangent Basis" on in Debug > Rendering, create a prim, create the default new script (anything with a touch event suffices) in its contents, and hold the alt key down with the object edit window open (whether or not the object is selected).
Observed results: The prim has edge lines (normals?) for each polygon.
Expected results: The edge/normal lines should appear without needing a scripted touch event.
Edit: Also happens on the root prim in a linked set with NO scripts in it or the entire object. Weird.