Testcase in WYSIWYGNestedTMLInHTML
Expanded testcase with LeftBar-example.
Like TWiki, WysiwygPlugin
uses regular expressions to try and make sense of the input and generate HTML. Unlike TWiki, WysiwygPlugin
has to try and keep % variables in the source, which leads to this sort of situation. The REs simply can't make sense of the above code, because you are using double quotes inside double quotes. If you change the outer quotes to singles, it should work just fine.
Added a documentation caveat.