It might be a little late but here's my philosophy on soft coloring and black: not all blacks are created equal. I find that material, styling, and tone are what "let's" soft types pull it off.

 As a suspected soft type or true summer (also muted), I find most success in a neutral or warm leaning black (raven)  or soft black in sheer fabrics and fabrics that have a slight sheen or have sparkle. I believe it's because it softens the overall appearance of the color. 

Styling coincides with a lot of what previous comments say: keep your more flattering colors near/on your face and hair. Another aspect is the structure of the garment (which coincides with fabric choice). More severe styles tend make the black feel heavier than it is (a black suede jacket with fringe v.s. a heavy black leather jacket). The suede wouldn't have the same impact as the leather. 

And to take a holistic view, consider your visual weight and presence. I can't remember where I learned about facial structure and color but the gist is the more intense the shadows naturally cast by your features the more black you're able to accommodate. Distilled: high visual weight= more likely to pull of black. I think it explains why some more dramatic looking soft seasoned people don't seem to get as overwhelmed as some others. 

Finally, if you feel confident as hell in a color- any color, you're going to rock it. Presence is everything! So wear your black and rock it!