You know your own username and it is actually not necessary to get this constantly in the login/logout-bar or topmenu-bar.
The avatar itself would already suffice and it would be quite nice to get the username to be shown by mouseover the Avatar.

Exactly what I have created in my forum and if you want to adjust this in your forum also, this is possible with CSS only. So it is cloud-friendly!

Before the adaptation and after the adaptation when you go with the mouse over the Avatar:
https://www.vbulletin.org/forum/attachment.php?attachmentid=156679&stc=1&d=1508173935

After the css changes:
https://www.vbulletin.org/forum/attachment.php?attachmentid=156680&stc=1&d=1508173935


/*hide-show username in main-navbar*/
#lnkUsernameMenu span.b-comp-menu-dropdown__trigger-username {
display:none;
}
#lnkUsernameMenu:hover span.b-comp-menu-dropdown__trigger-username {
display:block;
}


If you would like to do a fade-in and fade-out effect you could take a look at my forum.
I have another css-snippet there: hide-show username in main-navbar with a fade-effect (https://vbulletin-forum.de/forum/anpassungen-module-und-erweiterungen/templateanpassungen/156-benutzername-in-der-anmelde-men%C3%BC-leiste-nur-beim-mouseover-anzeigen)
The most content is literally in german, but I will try to translate it all.

Take a look at:
vbulletin-forum.de (https://vbulletin-forum.de/)