Suggestion - Make people post something in the giveaway description.

Right now, people who create GA can have the choice to not post anything in the giveaway.

So, some members, especially new ones, leave an empty description and people assume it's fake even though it may not be.

This way, the gifters would have to say something about their giveaway. And if it is real, I'm sure it would be something like "I have this game", "Steam key", "Steam gift". This would stop people from calling out. Even if it is in Russian, German, French, Korean, Japanese, Chinese, someone would translate it.

Usually it's the lack of information which causes people to think a GA is fake.

http://www.steamgifts.com/forum/2m4l3/this-is-exactly-why-we-dont-call-out-fake-on-giveaways/page/31337