I actually think moderating trades is not a bad idea, as many people get demotivated by the constant stream of unbalanced trade offers, and they decide to simply stop trading. As a casual trader I find myself trying to make fair trades (or trades that favor the other a bit) but constantly get declines and mostly get offers that are balanced too much in the favor of the other. I've thought about stopping myself every few months and I actually won't recommend trading to most of my friends because it simply takes to much effort to get (fair) trades. I do think there's probably a better way to improve the situation, for example by assisting people to trade based on value (first) and ratio and by offering better offer functionality.

I think there's a pretty big problem in the fact people value their own games higher and games of others lower, ignoring the value on gg.deals and therefore everyone is mostly wasting their time in making and declining offers. By giving more automation functionality, for example an option to auto accept offers for a selection of games, as long as the offer is similar in terms of value (and to some extent ratio), casual traders could trade so much quicker and easier. A bit harder because of security, but if you could also store keys for that selection of keys, that selection of trades could be instant. It would save time and would make trading for casual traders an enjoyable experience. I'm sure that functionality like this would attract a lot more people to trading.

PS: I don't mind trading with retraders, but for casual traders it would really be good if they are aware of how retraders trade - that they usually have a bigger selection of games, are quicker to respond, but want trades to be more balanced in their favor.
PPS: I'm new to this website and still figuring out the options, but compliments to the creator for making it look so good.