&gt; What do you mean by &quot;correct&quot;?<p>I mean this from the standard: &quot;Nonspacing combining marks used by the Unicode Standard may be exhibited in apparent isolation by applying them to U+00A0 no-break space. &quot;<p>You can have valid Unicode that doesn&#x27;t do this. But it&#x27;s not intended to represent the character as some kind of textual thing. It&#x27;s intended so that you can build up Unicode strings sensibly. Same idea as allowing mis-matched surrogates.