I don't know if this is a thing that has been already reported before or if I should do it on any of the provided specialized threads about it, but I casually found out that when I click on some series' reviews within the "useful" option in my phone (where I am logged out) show as already marked where I am logged in (in this case my laptop) and I cannot "undo" them (as long as I'm logged in, the ones I do click on, I can undo them). I'm sorry if my wording seem a little confusing.

Basically what I want to know: is this a thing of the ip address? Since my phone and my laptop share the same ip, they show as I clicked on them even when I was logged out?

Anytime you mark a comment as useful while logged out, it will use your IP to identify you. You cannot undo the ones that you do while logged out.

When you are logged in, it will use your user ID, so you can undo those.

The reason we do it this way is because there's no way to tell whether you are the person who originally marked a comment as useful if you are logged out. Several of our users come from countries that funnel all their citizens through single IP addresses.

We could potentially solve this by just removing the ability to add useful status if you're logged out.