The way the voting system works at Reddit encourages group think and bubbles. All it takes is five more down votes than up votes and a comment or post essentially disappears from view. It's a design that actively avoids debate.
Suppressed debate is almost universally due to biased/captured moderation teams aggressively using bans.
People shouldn't be blocked from commenting because their karma goes negative. Spamming, hateful talk, etc should be a completely different system. Just because what you say is unpopular (in one place mind you) doesn't mean your words should be hidden.