Hi there, the very same issue exists in Czech for example: test(y) results in “test 
”.
Also note that another solution is to simply use the XWiki’s verbatim notation: test{{{(y)}}} results in “test(y)”. So I think it would be useful to have this verbatim option among the out-of-the-box styles available in the WYSIWYG editor’s “Styles” combobox for regular XWiki users (need to investigate Adding custom inline styles to WYSIWYG editor otherwise…).