If i remember correctly, the original issue was that the SG in the DT was too high, and the thought was by mixing back some salt with the fresh RO-Di water, this would lower the SG in the DT more slowly, but only if he were using DT water, not adding more salt to the sytem. apparently this wasnt having the desired effect quickly enough.
I agree that the ATO should only be fresh RO/DI and shouldnt have any salt in it at all. Further more, this would only serve to keep the SG where it is, and not lower it, cause the salt isnt leaving the system with the evap, so, fill the ATO with fresh, and then each day take 1-2 gallons right out of the DT and dump it. Over the course of a week or so, this will lower the SG in the DT to where it should be.
This only works if you remove some of the saltwater thats in the system, otherwise, the level wont drop.