I think the OP is just venting about someone who shows constant bad form on the for sale forum. Corey said "i'll take it" in a thread of mine and even sent money to my paypal. Then I packaged the knife up right then and there (I keep USPS boxes and labels at home) 20 mins later he asks me to refund his money, which I did. The purchased package cost me a couple dollars or something, I didn't mention it, and that was that. I guess he just found another knife he would rather buy. It kinda pissed me off, and really irritated me. I think he just changes his mind a lot, not the end of the world. I have purchased a couple knives I thought twice about or found another deal on and still followed through with the initial purchase because it would have been a selfish move to back out of a deal I posted "i'll take it" in.
I think that if you post "i'll take it" in a thread, it screws the sale up for the seller if you back out. Don't say you will take it if you don't intend to buy it. At least deal with it via PM.
I don't think I would sell another knife to Comeandtakeit. Unfortunately, changing your mind, low balling people and inconveniencing them aren't grounds to get kicked off the forum. It's just part of selling to some members here.