Are there checks in place for verifying user emails?
Recently, I accidentally ended up creating a new account, when I briefly deactivated this one but wanted to get an evaluation of how much German I know (and so took a placement test). When I went to my email, I noticed emails from Duolingo that assumed that the email owner had indeed created an account on this site. (There was no "Didn't make an account on Duolingo? Click here to have your email removed." option. Nor did I have to do any sort of email verification for my account.)
Since I did in fact own the email in question, this wasn't an issue (although because of this, I had to manually go deactivate the other account I'd accidentally ended up with). But I'm slightly troubled that there's no check in place -- at least not a very obvious one -- for making sure that users own the emails they list themselves as owning.
Yeah, but if that were to happen, I'd end up with an account on Duolingo that I didn't actually want, and while I have the option of deactivating it, this doesn't actually seem to delete the account. Moreover, the same could be argued of almost any other service one signs up for by email, and those often have verification checks...