People trying to scam people in mmo's is a thing badly enough always present.
So better always stay aware of it.
Things i've learned myself of the years are:
when i trade something valuable with someone else i really know that char.
If i need to trade with someone's alt, i hope they've told me there name before
they swapped in doubt i always pm the alt to ask there name.
If i've doubts on it i never trade.
And if i see a char never seen before but sounds like a char i know believe me
standardly don't trust it, most players don't reuse there name, and the few who
do mostly will tell u.