Buying a steam wallet code can screw you over, if the seller used a stolen CC.
But can buying a steam gift implicate you in any way ? If the seller used a stolen CC, on maybe a new account, to buy a gift and give it to you ?
Short answer is: no
The long on: Steam has these problems every day and they usually do not revert trades. How do I know this? I used to trade TF2 items daily. There was a very big incident a few years back. To understand this you have to understand a bit about tf2 trading. Valve sells keys via the market for cash, but you can also trade them for other items. One of these other items is called "buds" and has a value of several keys (lets say 20) because its old and rare and you can no longer get it. Over a period of several days the price for buds rose rapidly because someone was buying all buds even at high prices (25 while 20 was normal) while at the same time the buds for USD price was falling because someone was selling buds cheap for USD, paypal, wester union, not BTC AFAIK, because it wasnt commonly used among tf2 traders back then. It turned out that this was a money laundering scheme.
#1 use stolen CC to buy keys from valve
#2 trade keys for buds
#3 sell buds for USD/other currency
While valve does not support the trading for items (or currency) outside the steam system they do not revert the trade. Why not? Well for one there are items worth 5000USD. If you would revert such a trade you would have to create a copy of the item (a dupe) thus reducing the price of all items in circulation. This is only done if the victim can prove that it was a scam (e.g. trojan). Dupes a frown upon by traders and are (sometimes) worth less. The other reason they do not revert the trade is that each trade can result in more trades.
#1 A buys a game with a stolen CC
#2 A trades game to B for e.g. 20 keys
#3 B sells game for .05 BTC
#4 A does 15 trades, 10 for 1 key each and 5 more for 2 keys each
#...
#99.999 Valve figures out the CC was stolen.
Theyd have to revert not only the single trade that was not legit (buying the game) but all resulting trades. They would constantly piss off everyone that is trading with steam and make that option basically useless.
So if you buy a game on steam from someone that used a stolen card it is not your problem.
I don't think anybody is accusing him of selling stolen goods, but the possibility is there and just because the items haven't been reversed yet doesn't mean they won't in the future is all I'm saying, but remember, if something sounds too good to be true it usually is (though of course there are always exceptions).
The thing with steam is: steam-money is worth less than regular money. Its "pretty easy" to make 20 USD worth of tf2/csgo/dota2/etc. keys a day if you have a good nieche and a few regulars, but its not as easy to get the money off of steam. The tf2 keys I mentioned above are sold for 2.49 USD[1] by valve, for 2.42 USD [2] by others on the community market and for 1.70-1.95 USD for BTC. IMHO its very likely that said user is getting the money other big steam traders are earning out of steam for them and gets a cut of the profit.
[1]
http://wiki.teamfortress.com/wiki/Mann_Co._Supply_Crate_Key[2]
https://steamcommunity.com/market/listings/440/Mann%20Co.%20Supply%20Crate%20Key
