<v:variable.set name="cantons" value="{0:''}"/>
<f:for each="{records}" as="commun" iteration="iteration">
    <f:if condition="{commun.communesRelatedFrom}">
        <f:for each="{commun.communesRelatedFrom}" as="canton">
            <v:variable.set name="cantons.{canton.uid}" value="{canton.title}"/>
        </f:for>
    </f:if>
</f:for>
<f:for each="{cantons}" as="canton" iteration="iterator">
    <f:if condition="{canton}">
        {canton}<f:if condition="!{iterator.isLast}">, </f:if>
    </f:if>
</f:for>
<v:variable.unset name="cantons"/>