Multiple channels in a single RSS xml - is it ever appropriate?

Question

A typical xml file for an RSS feed starts with an "rss" element on the outermost level, and usually has a single "channel" element within it that represents the "feed" or "channel." Is there ever a situation where it is appropriate to use multiple channels within an element, like the following?

<rss>
    <channel>
         ...
         <item> ... </item>
    </channel>
    <channel>
         ...
    </channel>
</rss>

Answer 1

From here:

Subordinate to the <rss> element is a single <channel> element, which contains information about the channel (metadata) and its contents.

So there not only is no use case for that – it isn't even allowed.