My experience of open source projects is that people dish out +1's freely and are reluctant to -1 as it signifies conflict. +1 is arguably the more ambiguous for that reason as it can mean "I didn't read the issue but I like you and what you're saying at a glance looks non-insane" or "meh" or "I love it". You're really underestimating the ammount of politics that can factor into these things, people will +1 something that they 90% disagree with because of who's saying it, don't kid yourself otherwise.

Nobody really cares if you +1 something crazy, maybe you were just feeling agreeable that day, or you misunderstood the comment. But if you -1 sensible things you're going to get a bad reputation pretty quickly.