This is because this char is not compatible with your codepage. If you try Unicode, for example, it will be ok. Otherwise you can insert it only to <literal> field.
But we are going to change this in eZp 3.9 and make it possible to use foreign characters.
I tried it with "Insert literal". But it's the same. When I put the sign in it, it will be channged to ? and when I put in the html-code I will the the html code and not the sign I want to use.
Is there no other way?
Linux is like a wigwam; no windows, now gates, and apache inside!
