I remember checking whether I would use std::deque, and I don't remember exactly why but I decided to implement this other system instead. I think it was because you can invalidate pointers with it if you delete somewhere in the middle, either manually or by calling an algorithm with it.

Of course you have the option to just not do that in your code, but it's nice to have a hard guarantee that this can never happen, even by accident. I could have used a deque as a backend and wrapped it in the class, though.