I'm speculating, but I think the big difference is the barrier to downvoting something here is greater. If you say something controversial over at Reddit there

I'm speculating, but I think the big difference is the barrier to downvoting something here is greater. If you say something controversial over at Reddit there is a substantial chance you get piled on and labelled a troll, unpopular positions cannot be expressed without the risk of no longer being able to participate. Anything you suspect will generate something other than a bland, mildly positive response is too risky to express.