Some have talked about it and laundry det. back in the fall I believe. do a search for "laundry" or "fabric". Two issues I can think are (1) it may leave a residue if not well rinsed, (2) may counteract the effects of the SH, not sure of the PH of fabric softner.
I know Chris Tucker recently posted a article of how washing machine cycles first dispense detergent so the enzymes can work before the SH is dispensed to disinfect and bleach out discoloration. If mixed concurrently, the SH fights against the enzymatic action of the detergent.
Yes I've read about the laundry detergent. Fabric Softener has a lot stronger smell than the detergent and I've notice adding a little softener when washing clothes with bleach that it masks the SH smell completely. Just not sure if it would apply to a larger and stronger batch of SH.
Arm and Hammer laundry detergent with baking soda does a pretty fair job of masking the smell. It does take the largest size bottle per 100 gallons of mix, but the smell changes from a strong bleach smell to the smell of a laundromat.