User blog comment:MisterWoodhouse/Resolving your overlapping username on Fandom and Gamepedia/@comment-38118372-20200423103901/@comment-24036697-20200423173255

"If you already have an account for both platforms AND the username is the same on both, you have a username conflict that needs to be resolved"

Note the uppercase and. If your usernames are different in both places, you shouldn't do this.