RSS-feed insertion via {{rss>http://xxxxxxx.yyy}} results in HTML validation error.
Can be confirmed by validating the following page:
http://wiki.splitbrain.org/wiki:rss
(holds also for develepment snapshot of 2006-08-23).
The reason is that the following html is generated: <p><ul>...</ul><p>, while <ul> is not allowed inside <p>.