I believe Reddit has the advantage that small groups run the individual subreddits and few people associate the garbage in a reddit like
Drew (and to a lesser extent me, as primary admin of a fark off-shoot) is faced with a nearly impossible task of keeping a coherent standard of moderation across all topics. Someone who trolls political threads might be a positive contributor when discussing cars or beer - reddit's model facilitates that better.
The other problem is that the user base changes over time. Misogyny in paticular has probably driven away thousands of fark users, but adding the rule now is too little too late - those users are unlikely to return and the users that are left are (on average) going to be far more resistant to the new rule.
Is the type of trolling that exists on other sites that are "community moderated" tolerated in the garbage-type subreddits? I honestly haven't been able to tolerate the threaded model for comments on reddit to get very involved in any threads/subs.