Lets be honest here. If at the time of posting, Jangoo had nevegative karma, I suspect many of the users would consider this a revenge attack or an attempt to be back normal.
But now that Jangoo has positive (or neutral at the time of posting) karma, people are taking this much more seriously (not to mention his highly ordered and well spelled/punctuated arguments.
The karma system is absoultely fine, to reward people for things that benefit the community, and inform them when their criticism is more destructive than constructive. The problem is the people. For example, if I created a card, and one person told me it wasn't worthy of being implemented in the game, I would be very tempted to give negative karma. In a way, it would be an indirect attack, as they would never know how it happened. The other problem if people judging based on karma. If this person did get negative karma, people will be less inclined to see his point of view, even if it is the same as before. Likewise, people seem much more happy to agree with a person with high karma (this is definitely not always the case though).
I think this debate will not reach a conclusion easily, as there are valid points on both sides. For now however, I will side with Jangoo, but to show the positive affects of karma, I think I will +1 him as well, for his strong arguments