Kim Eana (IU's lyricist), Park Yohan (IU's dancer) and Hanteo manager have コメントしました on her 写真 (I'm way too lazy to scroll all the コメント looking for もっと見る people I know.)
She is also following several people, like Coordi Noh, that require approval to be followed.
IU's confirmed Instagram account: link
[UPDATE] IU's former producer, Cho Young Cheol, confirmed the account on his twitter via his Instagram: https://twitter.com/cho072/status/563714370463862784 and IU（アイユー） replied.
Translation here: link
写真 caption translation:
ee ji geum (wordplay of ‘Lee Jieun’, meaning ‘this now’) Instagram. Why does everyone add # at the back?
trans source: link
写真 source: link