I don't think trading reviews is a polite thing for devs here. Pls, just look trough games and give them reviews by yourself. Trading is not cool!

I see trading reviews as a way to let your project be known even in a small way. There are 350 entries and it is not humanly possible to rate them all by one person, so I find this a way to rate games that maybe go unnoticed for different reasons. I'm honest with every game I review, if I think something is not right I tell the developer what could be improved and what can stay. I also played some games that interested me in the submission tab but having a smaller group of entries to choose from can help manage time and make your game be played by more people.  

Personally I think trading reviews is a good way to “advertise ” your game. Just like Fettenderi I am also honest with the games that I review. 

I'll be honest, I'm not a fan either. I prefer games to be found and played organically. I don't like when people hold  votes hostage, ie: You vote on my game and then I'll vote on yours. Sucks the spirit out of the jam.