[em-bee]

which editor does that? space width is defined by the font, and normally you use monospace fonts. i am unfamiliar with any editor that allows you to choose a different font for spaces. besides, it would only work for indents, it would mess up any alignment of code into columns.

[SAI_Peregrinus]

None, but it's clearly possible to add since such handling is already present for tabs in almost any editor. I merely mean that there's no technical restriction.

[efilife]

But this option already exists for tabs that are pretty much built for this purpose. It's like adding a fifth wheel to a car because there's no technical restriction even though 4 work fine