The IDLE debugger has subwindows to display name-object bindings for locals and (optionally) globals. They have a gray background. Text is black, object strings get a white background box. The issue is that the white box and text for each name is slightly raised relative to the name. This is somehow especially noticeable to me for something like 'd = 3', resulting in
d3
with 3 boxed and raised a bit so it almost looks like a superscript.

This is a fairly minor issue, so low priority now unless trivially fixed. But it should be part of polishing IDLE. I am hoping that this is not a tk bug that is terrible to work around.