It's very, very, veeeeeeeeeeeery difficult people understand the diference between 'username' and simple 'name' (nick) in portuguese. Telegram says in portuguese: 'Nome' (nick) and 'Nome de Usuário'. There are one big problem in it: All we make enormous confusion between them. The better thing to do is change 'Nome de Usuário' for 'Link da Conta', 'Link do Perfil'. In this way, the major, or almost people will knows that 'LINK' is not a name, or nick, but a REAL LINK, a REAL ADDRESSE of an account, page, site... In Brazil people knows and understand what I'am saying here. Here, for exemple, we use to say: 'link da página' (page's link), or 'endereço da página' (page's addresse).

'Nome de usuário' is a standard. It's certainly not difficult to understand, especially because all apps and services name it like that in Portuguese.