ice:panelCollapsible header styling issues

Had a problem this week with styling nested ICEfaces collapsible panels. (ice:panelCollapsible): the top panel would be styled, but the children's headers didn't get the neat open/close buttons from the default rime stylesheet. Custom styles wouldn't get recognized either.
After hours of digging around in CSS and ICE forums, I finally realized (thanks to the JIRA 3209) that the problem was not with the style, but with the layout. The content of header must be contained in a <div> (or an ice:panelGroup), otherwise the style doesn't get recognized. It doesn't have anything to do with nesting, I just happened to copy the top panel from elsewhere, and didn't pay attention to the wrapping panelGroup.

<ice:panelCollapsible expanded="true">      
 <f:facet name="header">
  <div>
   <ice:outputText value = "Grocery Panel"> </ice:outputText>
  </div>
 </f:facet>
 <ice:panelGrid columns = "1">
  <ice:outputText value = "Food stuffs"> </ice:outputText>        
 </ice:panelGrid>
 <!-- Nested panel 1 -->
 <ice:panelCollapsible>
  <f:facet name="header">
   <ice:panelGroup>
    <ice:outputText value = "Fruit Panel"> </ice:outputText>
   </ice:panelGroup>
  </f:facet>
  <ice:panelGrid columns = "2">
   <ice:outputText value = "Apple"> </ice:outputText>
   <ice:outputText value = "Orange"> </ice:outputText>
  </ice:panelGrid>
 </ice:panelCollapsible>
 <!-- Nested panel 2 -->
 <ice:panelCollapsible>
  <f:facet name="header">
  <ice:panelGroup>
   <ice:outputText value = "Vegetable Panel"> </ice:outputText>
  </ice:panelGroup> 
  </f:facet>
  <ice:panelGrid columns = "2">
   <ice:outputText value = "Cucumber"> </ice:outputText>
   <ice:outputText value = "Potato"> </ice:outputText>
  </ice:panelGrid>
 </ice:panelCollapsible>              
</ice:panelCollapsible>

Dev environment: ICEfaces 1.8.2, MyEclipse 7.5, Liferay 5.2.EE