I think the original question needed more clarity. It does "pass" DD in the sense that it outputs DD from the internal sources like Netflix. This makes sense.

It doesn't pass DD from HDMI and then output it to optical. I feel like this is a no brainer. It's not a receiver or a video switcher. Do you really expect it to have this function? It's not an HDMI-downmixing chasis card from Savant or something. Come on guys. You are asking a little much. Why would you hook up equipment this way. If you want DD, get a receiver.

As a passing note, do you think your Sonos sound bar is giving you dolby digital? Even if you feed it opti from a tv, you aren't getting DD. You are getting sonos matrix / sonos (best guess) processing. It's still pretty good, but it's not true discrete. Last time I checked the DD spec, they don't have anything standard (or listing for that matter) for wireless rears (or really for a soundbar in general).

So i guess the original question, does Samsung output DD from opti when feeding it DD from HDMI, the answer is not only no, it's moot. You aren't getting DD from your Sonos or really any other device that isn't a receiver. In case you think I am just being pompous, which I am not, please show me the DolbyD logo on the Sonos box or equipment.......