We had ToolBar like this in gxt version 2.2.6 :

ToolBar toolBar = new ToolBar();
final Status gridPageSizeLabel = new Status();
gridPageSizeLabel.setToolTip( "Change the number of rows to display in the grid." );
gridPageSizeLabel.setText( "<span style='font-weight:bold;'># rows:</span>" );
toolBar.add(gridPageSizeLabel );

and html used for label used to render fine

for 2.3.1 it does not work, so I changed it to setHtml, but still html is not getting rendered