The feedvalidator chockes because it is too large, unless you set days=0. I guess the BannedContent page just ruins it. [1]
The feedburner also chockes on size or timeouts unless you use days=0. [2]
The burner will take the feed from the test wiki, however. I assume it also chockes on size.
There's also a new page, RssExclude, that lists pages to be excluded from the feed. This is important for very big pages such as BannedContent. To circumvent this, use the exclude=0 parameter.
Yeah. I think 220KB is a bit large for an RSS feed. ;D