I think if you stick with a lightweight break-a-way collar, this shouldn't result in matting the hair down. These are made from different materials but nylon is common. Here are a couple of links to these collars, but I am sure you can find other brands and types at your local pet supply store.
Get a break away collar. When it's on the cat, check the collar every so often to make sure it didn't tighten because it's hard to spot from plain view underneath all the fur. After a long time, it does begin to mat the fur but be sure to comb or brush that part of the cats neck to prevent tangles from forming.
I don't know about matting but all of my cats that have had collars have eventually lost the fur from around their necks. The collars weren't too loose or tight or anything. Having said that, it took a few years for this to happen.
might be best to not have collar on kitty. both of my cats are indoor cats, and when they are inside at home, they never wear their collars.
when i take them out to go some place (my mothers) or to the vet, then they wear the collar. aside from that my cats never wear a collar. If its for short and temporary reasons like maybe taking your cat to the vet, its not long enough to really affect your cats fur in any negative way..i think..
My kitten is a semi-long haired (half) Siberian. I graduated introduced him to a normal breakaway collar when he was 4 months old, and got him to wear it full time when he was 6 months old. You should be able to fit 2 fingers between his neck and the collar, and make sure you loosen it once in a while if he's still growing. The collar hasn't damaged his neck fur at all.
However, the hair on his neck may be parted (kind of like human human). Because of this, I will take off his collar on the weekends so I can brush him thoroughly and so that his hair can look "normal."