Well, nothing says that it should be a democracy. But there is discord how moderators manage their communities and what support reddit could add. e.g. there are subreddits that have removed downvoting through CSS, so it is still possible to downvote with apps or changing the CSS. It should be possible to add that as a setting to the subreddit that makes it impossible to downvote.

But like I said it isn't a democracy, reddit can decide to not implement that and explain it to the mods why not.