I finally found out, why Konqeror never discovered the RSS-Feeds on TikiWiki pages. That was actually a no-brainer. The content-type of the RSS-Feeds was set to 'application/xml', which is no correct content-type at all. It has to be 'application/rss+xml', 'application/rdf+xml' or 'application/atom+xml' depending on what type of feed it is. Well, committed for now to CVS with just 'application/rss+xml' for all of 'em.
And I added all the available feeds to the header of this site - check your shiny RSS-icon in your browser! ;)