Can I use bleach when laundering a down comforter? Generally the advice when laundering such items is to use a mild detergent, since the down otherwise may lose its natural oils and dry out quicker. Does the bleach strip the down of its oils? Does bleach cut grease in general? A lot of questions, but I know you’re the right one to ask!
All the advice you quote is correct: use a mild detergent to avoid removing too much of the natural oils, and probably a warm water wash for the same reason. Liquid bleach attacks stains and soils and is not particularly good on greasy/oily stains. These require surfactants and solvents to solubilize/dissolve the oils from fabrics. These ingredients are found in detergents, thus the “mild” detergent choice.
First, I want to be sure all parts of the comforter can be bleached. I find that a lot of colored items can safely be bleached. To find out if your items can safely be bleached, I recommend consumers do the quick Bleachability Test (2 tsp. Clorox® Regular-Bleach₂ with CLOROMAX® in 1/4 cup water; apply a drop to the colored portion on a hidden area like inside seam, hemline or cuff; wait 1 minute and then blot with towel); no color change means it is safe to use bleach on the item.
Want to proceed? I would also consider doing a quick liquid bleach soak (1/4 cup Clorox® Regular-Bleach₂ with CLOROMAX® in gallon of cool water for 5 minutes), then wash immediately in warm water using detergent and 3/4 cup Clorox® Regular-Bleach₂ with CLOROMAX®. Check before drying to insure complete removal in case something needs additional treatment. To complete the treatment, consider air drying.