I'd really love to be able to insert, for instance, ​ or <wbr> or any other codepoint that will make the documentation more expressive or look nicer.
For instance the word break character is really useful to put between parts of a long file path so that it can break at slashes on mobile devices.
I can't seem to find a syntax that allows anything other than the ones listed at https://www.doxygen.nl/manual/htmlcmds.html
I even tried pasting the (invisible) characters directly into my c++ source code, but Doxygen didn't like that.