Thanks for the tip and sorry for the late response. This seemed promising at first but let to all kinds of strange behavior. Code-blocks that are part of a list item turned out to particularly painful, as here "Finally, you can use ‘-i’ to preserve the indentation of a specific code block" means that an additional five (if I remember correctly) spaces appear out of nowhere (only for code-blocks, example-blocks behaved as expected (or at least in an reasonable way)).
I am going to use the `org-export-filter-final-output-functions` approach suggested earlier. I might at a later time come back here to discuss the issues I encountered, but right now I am too frustrated about the difficulties I encountered to do so. (Texinfo is painful enough to deal with, if now Org (resp. its texinfo exporter) also acts up, that's just to much to take.)
