When executed from the workbench:
unexpectedly returns an empty result set on the following test dataset.
If directly submitted to the HTTP endpoint like:
works only if charset=UTF-8 is explicitly stated in the Content-Type header.
AFAIK that's not customary and according to the HTML5 specs (note at the end of § 22.214.171.124 URL-encoded form data):
Parameters on the application/x-www-form-urlencoded MIME type are ignored. In particular, this MIME type does not support the charset parameter.