online trading is all about trust.
if u dun trust each other, then dun trade lor..
juz buy from a local store would do..

as simple as that

PS - lelong oso got so many scam and con case, even they got ic validate feature

well, one more reason is this is a forum, a place to sharing and changing informations/experiences, discussion and gaining knowledge..

its not built specially to trading..like lelong and ebay..

thats why there are no implementation for things such as mentioned above..