Spam is filed in two different mail boxes: Spam and Junk

I am using Apple Mail on a Retina Display MacBook Pro, with all applicable software (Mail, SpamSieve, Mac OS, etc) at the most recent version. I recently updated from Mac OS 10.8 directly to 10.9.1 (I avoided the original 10.9.0 release due to reported problems with Gmail.) I have two IMAP accounts (Gmail and iCloud) and one POP account. Mail’s Junk filter is turned OFF. (And, FYI, I have been a contented user of SpanSieve with Apple Mail for years.)

A lot of my spam emails have the Apple Mail junk banner at the top, even though the Junk filter is turned off. I think I read somewhere that this is a feature, not a bug. Is this correct?

More importantly, with SpamSieve running, my spam is sorted into two different mail boxes: some go into the Spam mailbox as expected, others go into the Junk mailbox. (The Junk mailbox exists and is visible even though the Junk filter is turned off.) I think it is my Gmail spam that ends up in the Junk mailbox, but I’m not 100% sure about that. I’ve checked all my Rules in Preferences, but there’s no rule that I can find that says anything about the Junk mailbox. The Junk filter is off. So I’m flummoxed. Is this “normal” behavior? If not, is there a way to fix this so all spam goes in the Spam mailbox? Or should I just accept life as it is and move on?

Yes.

Yes, it’s normal (on Mac OS X 10.9) for Mail to display Gmail’s “Spam” mailbox as “Junk”. Mail cannot prevent messages from going there, but you can turn off Gmail’s filter if desired.