If we really didn't want "personality voting", we possibly could simply block if there was a counter for how many votes any monk casts on other single monks. If that reaches 30% of the monks votes on any day, he could still spend votes on the same other monk but those votes would go away without affect XP (or even reputation).
Remember that for the first few levels 30% of the votes may be just less than 5. Also consider this scenario: I read interesting post from A; I wonder if the other posts from him are just as good, I check a few and yes they are, so I upvote them too. The same could apply to a particularly bad post: but then you may question about whether it's ethical to go hunting for particularly good or bad nodes for upvoting or downvoting respectively as opposed to stumbling into posts "randomly". My answer is that there's limited randomness anyway, and that you always search posts in some form or another, and eventually that there's nothing unethical in doing what I described as long as votes are applied with consciousness: i.e. upvote if an upvote is deserverd, downvote if a downvote is deserved, period. Is it worth to loose this freedom? IMHO, no!