code: protected boolean mayEnterEmphOrStrong(String chars){
      	if( !isLegalEmphOrStrongStartPos() ){
              return false;
          }
  
          Object parent = peek(2);        
          boolean isStrong = ( chars.length()==2 );
          
          if( StrongEmphSuperNode.class.equals( parent.getClass() ) ){
              if( ((StrongEmphSuperNode) parent).isStrong() == isStrong )
                  return false;
          }
          return true;
      }
docs: This method checks if the parser can enter an emph or strong sequence
  Emph only allows Strong as direct child, Strong only allows Emph as
  direct child.