Thread:Extension talk:RSS/flickr tag not parsed inside MediaWiki:Rss-item/reply (5)

For security reasons in the newer E:RSS versions, all tags are sanitized (i.e. removed or replaced by esacped versions) except Url links  and   depending on the two settings mentioned in the manual. Perhaps this explains your observation. It will certainly not be changed in short time, because it requires a new code change and security code review cycle, and we developers have no time at the moment.