LMTP and Sieve with <prefix><recipient_delimiter><user>

Hi there,

Dovecot's LMTP implementation and Pigeonhole Sieve already do support the <user><delimiter><suffix> format. RfC 5233, the Sieve subaddress extension, also offers <prefix><delimiter><user>.

Could Docecot's LMTP and Pigeonhole be extended to that effect?

Thanks & greetings,

Paul