Board Thread:Questions and Answers/@comment-90.221.228.185-20150511233505/@comment-3250527-20150805031643

In Japan, males are considered adults at age 16, and females at age 14, but pretty much, if you've graduated middle school, you're considered an adult. Also, first off, the anime is ecchi as a secondary genre (Season 2 just throws that into your face with all those Sugu close-ups), and the SAO light novels themselves have quite a few ecchi-like illustrations (the Progressive series especially).

The Wikia doesn't refer 16.5 as canon because of Reki's claims, and because of its location under a "fanfiction" header rather than something like "official works". (I haven't seen the WordGear site, so... just repeating what was told to me.)