I have a filter inside a rich:extendedDatatable (the same goes for rich:dataTable):
<rich:column sortable="true" sortBy="#{a.id}" filterBy="#{a.id}">
<f:facet name="header">
<h:outputLabel value="row1"/>
</f:facet>
<h:outputText value ="#{messages[a.id]}"/>
</rich:column><rich:column sortable="true" sortBy="#{a.id}" filterBy="#{messages[a.id]}">
<f:facet name="header">
<h:outputLabel value="row1"/>
</f:facet>
<h:outputText value ="#{messages[a.id]}"/>
</rich:column>filterBy works with message-keys. We have checked it.