Suppose you are Reuters. You produce a feed with BusinessNews. Not a non-ASCII character in sight. Your feed conforms to the specification, but contains some GUIDs which are not sufficiently unique. This may cause aggregators like RSSBandit to not show you items in feeds that you are subscribed too. Silently.
But again, another rare problem that occurs in few aggregators. Edge cases.
Now, view source on the business feed. The descriptions are completely valid and conform to the spec in every way. As you would expect in a business feed from a company like Reuters, may of these descriptions contain stock ticker symbols. Now subscribe to this feed (or perhaps this snapshot) in your aggregator. Look for the stock ticker symbols.
We have yet to find a single aggregator which will show the stock ticker symbols.
Not a single one.
This is called data loss. Silent data loss. We are not talking about unusual characters. Or the occasional item in a few aggregators. We are talking stock ticker symbols. In a Reuters Business feed. In every single aggregator that we have tested with so far. Silently.