I did not actually test this on the trunk version until now.
It seems that a change in revision 61425 caused this problem to not occur anymore for blog RSS feeds.
The friendly url mapping was changed from
<ignored-parameter name="p_p_cacheability" />
So now the resource phase is used to serve resources instead of the action phase
This means that in LayoutAction this branch will be reached
request, response, PortletRequest.RESOURCE_PHASE);
Instead of this branch
Resulting in the problem disappearing regardless of strip filter settings
However the problem still manifests itself for these blog mappings, that where not updated
Also the activities portlet seems affected. It uses the mappings defined in
which also uses exclusive mode actions
and most mappings in com/liferay/portal/kernel/portlet/rss-friendly-url-routes.xml
this mapping file is used by the activities portlet
All of these should probably be mapped to the resource phase