is moving a message as simple as moving it from one users/user/Maildir/cur directory to another?
cur contains mails already fetched by a client (at least when using IMAP, emails are being moved from new to cur when the mailbox is opened, not sure with POP3, I don't use it). You probably want to move from new. Anyway, manually moving emails around might confuse the clients. The pseudonym redirection is a safer approach