The other platforms make dissent visible. Even if 30 people are screaming at me in the tumblr notes, I can see that 20 people clicked the little heart to like my post. But on reddit, I'm sitting at a -10 and I don't know if that's because ten people disagree with me or because 30 people disagree and 20 people agree. The little controversial dagger can be helpful with this, but only if the values are very close.

Add in the downvoting issue, and it's very easy to bury people with the feedback threat of "shut your mouth if you don't want to wind up muted" which...is what downvotes are. Subreddit karma is used in the crowd control official mod tool to auto-collapse your posts and send them to the bottom of the thread to die. A new user who comes to a subreddit and, say, wants to discuss ableism in RPGs(because they are themselves disabled and are interested in the subject) only to be met with heavy downvotes because reddit hates the word ableism is going to just walk away from that subreddit. And so views continue uncontested.