Reading the changelog for July 30th I saw an example of the new exchange rate widget.
In the example we see the query "what's 100 icelandic krona in loonies" which then promptly displays the currency widget with the conversion. However upon testing this I wrote "what's 100 icelandic króna in loonies", note the diacritic in 'króna' but the widget does not show up.
"Króna" is the official name of the currency and is hinted to by the wiki page and the sidebar:
Testing further I see that the query
"what' 100 salvadorian colon in loonies" displays the widget but using the real name of the currency with the diacritic: "what's 100 salvadorian colón in loonies" does not display the widget.
So it appears the currency conversion widget only supports the anglicized version of currency names and will not return results when using the "real" name.
While writing this bug report I also managed to trigger some other kind of bug: 
where it displays the Wolfram Alpha widget but with conversion results.
Was able to trigger that with the terms
"what's 100 salvadorian colon in dollars", "what's 100 salvadorian colon in usd", "what's 100 salvadorian Colón in gbp" and others.
I would expect the search terms with both anglicized and official names of currencies to show the currency conversion widget.
