I was not happy about this.
But then I realized that with my e-mail address come e-mail rights. Like resetting someone's password. And access to their account.
So I asked for a password reset to be sent to my e-mail. Then I logged into "my" account. Turns out some guy named "nelito" decided to use my e-mail address.
Well, guess who has a new username, e-mail address, and user profile?
My only regret is that this doesn't seem to be an active account, as this person has not posted any photos and only follows 3 people. But if the only thing that comes out of this is some dude named Nelito looking at his phone one day and seeing that his Instagram username has changed to "nelitoisandiot", that still pleases me to no end.