Buying BTC from a forum member is stupidity, even if the member has high green rating of trust your money can corrupt the person into giving up his or her account, we have exchanges for buying and selling coins, they are lot safer
It just means that it isn't enough basis to consider a person as trustworthy. You should check and verify things carefully because it's difficult to determine if a person's intention was good. There are various ways to buy bitcoin and buying from someone you just met online is a serious risk, especially when you're uneducated because there is a big chance that they will use that against you.