The username is a unique identifier of your account on this and all the other instances. It's as unique as an email address, which makes it easy for other people to interact with it.
Do you really want to delete <x id="PH" equiv-text="videoChannel.displayName"/>? It will delete <x id="PH_1" equiv-text="videoChannel.videosCount"/> videos uploaded in this channel, and you will not be able to create another channel with the same name (<x id="PH_2" equiv-text="videoChannel.name"/>)!