The rss pubdate format is the date time spec from rfc822 for email so is very widely supported. Cdata is supported in rss too — it’s in the xml spec so would be a bit redundant for rss to explicitly support it. You’ll find it in description elements very very often. I never understood why a link would not be a guid but the difference seems clear enough - use guid if you need a guaranteed unique idea and use link if you need a url to the list.