A couple of things. There are wads and fillers Both Dacron and kapok are wads they may look fuzzy and all when you put in in but at the moment that matters it compresses into a wad. The more harmful is Dacron because as John pointer out the explosion turns it into a gooey chunk that may have enough mass to cause trouble. Fillers are things like cream of wheat and some of the commercial granular fillers that are on the market. 
  There are two reasons to use a wad for smokeless. First on smaller cases like the 25-20 SS it keeps you from spilling powder into your action. This is a wad placed at the mouth of the case. They also have the secondary benefit of keeping the base undamaged. Charlie Dell reported that when he shot bullets with out a wad, that when they were retrieved the base of the bullets looked like little elves had been beating on the bases with tiny ball-peen hammers. The second reason is to control powder position inside the case. When the powder is kept in the same position in the case the ignition will be closer from shot to shot. Charlie recommended a wad placed .050” to .100” off the powder and the case rotated so the powder was oriented toward the wad and allowed to slump toward the base. This gave little to no ringing in his brass chamber testing.

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Both Dacron and kapok act as filler in the passive state. However at the detonation of the primer and powder they collapse in on themselves and are forced into a wad at the base of the bullet. Fillers such as Cream of Wheat remain a plug and do not collapse in on its self at the moment of ignition. That is why I consider Both Kapoc and Dacron and all other fluffy fillers wads. 

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