I don't think the voting aspect is as big of an issue as some here are making it sound. You only get one vote - up or down - on any one answer, so there's a real hard limit to how much you can do.
I actually played with this idea back when the site was starting out and there was a much bigger window for retracting down-votes... and in my experience, it really doesn't work at all on real, technical questions unless you're duking it out with someone else who posted essentially the same answer and neither one of you edit your answers. At that point, whoever sorts first has the edge on incoming votes, so if you down-vote them you can get that edge and the associated votes. Of course, if they spend their time editing and improving their answer, you just end up looking pathetic.
On more subjective questions, you might get a bit more mileage out of it. Since there's no objective "right" answer, down-voting your way up the list can put your answer in the path of sympathetic eyes without any extra effort required.
Frankly, I don't see the point. If you're scraping rep from populist answers on subjective questions, you're already involved in a much bigger "rep scam" than any of these little vote games. And if you're answering technical questions, rest assured that it'll catch up with you eventually...
Now... The comment aspect is something else. I assume he's talking about bad-mouthing other people's answers; I haven't actually seen much, if any, of this, so I won't try to speculate further on its efficacy other than to suggest that again, sticking to Real Questions is probably a good way to avoid it.