[Dovecot] Managesieve AUTHENTICATE with IDN using UTF-8 or encode into ACE?

Hey dovecot-users,

clients that speak telnet based protocols like http, smtp usually encode IDN (International Domain Names) containing UTF-8 characters into ACE (ASCII Compatible Encoding) punycode.

I am wondering what the case was with managesieve (RFC 5804). For example if I was using a username like "user@äüö.example.com" with the AUTHENTICATE command. Would that need to be encoded into ACE or be left in UTF-8? Reading section "2.1. AUTHENTICATE Command" or "4. Formal Syntax" suggests that quoted or literal UTF-8 is correct.

Thanks

Christian