There is quite a bit of confusion which maybe I can help clarify.
The CDSD was upgraded to CDSD Signature Edition. For most CDSD owners, the Signature Edition is identical to their units. The difference is indeed the badge to keep the look consistant.
In the case of the Positive Feedback review, the previous CDSD that was on hand was a very old unit which had some problems which might have been caused by a power surge. Indeed, the sonic differences reported were significant.
Most of what people are reporting with regards to the sonic improvements is really the DCC2e Signature Edition or DAC6e Signature Edition improvements. The CDSDse can be different sounding than some older units due to changes which had to be done due to vendors reworking of parts, such as transport mechanisms which change yearly. This is out of the control of any manufacturer that uses these parts. Whenever a drive mechanism is discontinued and replaced, there need to be software changes for the new drives to communicate properly. This is not something that we or other manufacturers want to go through, but the production of these drive mechanisms is not something that we (manufacturers) can control.
We are very pleased that Fbhifi and many others are hearing the very substantial improvements that were implemented into the new DCC2e and DAC6e Signature Edition models. Personally I agree with Fbhifi that CD is improved so greatly that it is very difficult to differentiate between SACD and CD.