As for labels, I meant that both OperaMail and Gmail have system of tags. However Gmail tags are treated as IMAP folders not using OperaMail tags. I realise that creating new tags in OperaMail may get out of sync with Gmail, but the the other way round - having labels from Gmail imported as labels to OperaMail should be possible to do.
Mailing list only looks at the List-Id: email header. Facebook is sending that in its emails, and that's why it gets its own "Mailing list" automatic entry.
Not that beautiful, I agree.