I think, non breaking space character (0xa0) is space.

Proposed patch (Core/CharSet.h):

-inline bool IsSpace(int c)         { return c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\v' || c == '\t'; }
+inline bool IsSpace(int c)         { return c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\v' || c == '\t' || c == 0xa0; }

You can test it with an EditString

someedit.SetFilter(CharFilterNotWhitespace);

And try typing 0160 on numpad while holding down Alt key.
Some users can be tricky.