Hello, As you see, my login is entirely made of numbers. But if you try to access to my profile, you will se the profile of someone else, unless you know my account ID.
What I want to say here is that there is a conflict between these two way of seeing a profile: by ID (in priority in the execution order) and then by nickname (more SEO friendly).
To fix that we have to chose between the ability of making account with only numbers, and accessing profile by two different type of argument in the URL. :(
I hope that it will help!