SOLVED:
Apparently you need to go into the database itself using PhpMyAdmin. Look for the wp_options table, find the rss_language value, and change it to da for danish (or substitute with the language code for your country).
Further information:
1. I use the Blubrry powerpress plugin for tagging my podcasts, but it doesn´t seem to support the language tag without modification.
2. I have no skills in php, but can edit/upload/download and otherwise customize things – so if you have a solution, please take this into consideration.
3. I am using the WP Modern Notepad theme.
regards
