Special characters available in summoner names (NA)

I opened a support ticket (#30168383) about the special characters available in summoner names.

https://support.riotgames.com/hc/en-us/articles/201752814-Summoner-Name-FAQ#h1q5

It says on the above page no special characters are allowed in names on NA except just yesterday I created one called Duô.

https://na.op.gg/summoner/userName=Du%C3%B4 http://i.imgur.com/8cDQY34.png

Support said this is an unintended bug but as far as I know it's been around for at least 6 months. Is this really a bug or is support uninformed as usual. In the latter case could that page be updated with the correct characters.