> My favorite unicode character is zero width space. One of its funniest properties is that it's not a whitespace.

My editor is configured to never show any character (except the one and proper newline) at less than the full-width of a regular character (in the monospace font I'm using ofc).

And if it's not a visible ASCII char, not only it's always shown at least at full-width, it's also shown as bold magenta on a black background. As the non visibe zero-width is empty, it shows as full-width on a black background.

Sticks out like a sore thumb.