Previously, I was under the impression that Jambler was merely a software or platform provider, like Wordpress or AWS. But after reviewing it more closely, it meets the definition of a mixer as written. My mind was especially changed when I saw this diagram from their website:


The diagram clearly shows that Jambler is the actual mixer. They issue the "letters of guarantee", they send the BTC directly to the final customer, etc. The partner is just a lightweight proxy in front of the true mixer, which is Jambler. Jambler "has a feature advertised for taking property, improving its privacy somehow, and then returning roughly the same type of property", and it meets the other two criteria, so it's a mixer.

(Maybe you could make the case that Jambler's actual customers are its partners instead of the final end-users, but even in that case Jambler is acting as a mixer for its partners. Jambler is the one doing the mixing. So it's still a mixer in either case.)

Since I had previously ruled that Jambler did not meet the definition of a mixer, and I've now changed my mind, there will be a short grace period: Jambler will be wordfiltered (and otherwise treated as a mixer) starting on April 22.