In Vim with iso-8859-1 encoding, when you press NBSP (NoBreakSPace) character (0xa0 in 8-bit ASCII), you see:
«| Es-tu là| ?| »
But with utf-8 encoding, you see by default a common space for NBSP.
Then, you can add theses lines in your vimrc to see it:
if &encoding == "utf-8" set list lcs=nbsp:· endif
And you can see:
«·Es-tu là·?·»