After reading both the thread and the article, I would say I agree with MOST of it, but not all. There were a few things about the article that I would strongly debate, especially having kept oscars and other lg central and south american cichlids, and after dealing with Hexamita disease many times over, in my own tanks and the stores, and with customers.
The way the article is worded allows for these debates, so I found it a good read. The things I would most debate is the info given in the thread. For starters, nobody should EVER have to do an 80% water exchange. In the case of my oscars, if I used that as an "easy way out" of the carbon issue, I'd have a water bill that exceeded anything carbon cost me in a year. 80% water exchange in a 220 gallon tank is A LOT of water. On top of the water bill, the electric bill would go up from the heater having to heat that amount of water every time I did the change. An 80% change in a large tank is both impracticle and expensive no matter how often you'd do it.
I will agree, carbon doesn't ALWAYS have to be used, if the bioload is sufficient to take care of total waste breakdown, and enough small water changes are done frequently, live plants are used to help with waste... meaning A LOT of plants to a few fish.
What I will say about carbon is that in some of my tanks I use it and some I don't, depending on the situation. The specific situation should help to dictate whether it is needed, not someone's idea or opinion of yes or no overall. For a beginner who doesn't understand the meaning of "natural aquarium" and how to create it, carbon is a good thing. For tanks such as my breeding tanks, where I never know when to expect more fry, it's a good thing because it's there to catch the extra waste when I'm not there. It soaks all the things that Blue listed, but also fish and plant waste, too.
There are dangers to using carbon if it's not used properly, though, and I won't skip those to get a point across. If it's not changed every 30 days, it can leak all of the pollution back into the water. If used long term, it can soak needed minerals out of the water. However, so long as it's kept changed on time and accompanied with regular water changes, which would need to be done anyways, it can be a very good thing in the tank of a beginner or in overpopulated tanks, breeder tanks, etc. Tap water contains all of those good nutrients that the carbon will soak up. If a tank isn't getting regular water changes and additions of tap water, even a tank without carbon will be in trouble at some point.
The trick or "secret" to good fish keeping without issues is really rather simple. Know what you're keeping, what it needs, and provide it. Don't overstock a tank, don't mix incompatible fish, don't put fish in the wrong environment, make sure that large fish have a large enough tank for their needs from the start so you don't hit the breaking points as they go through growth spurts, don't over feed, and do regular water exchanges and gravel vacs. Fish keeping is not an exact science, there are many ways to do each thing, but there ARE some basics that I consider to be the backbone of the hobby, and you simply can't get away with not providing it, such as I listed above.
One last comment before I go:
I believe that when people stop considering this a "hobby" or a form of entertainment for their own benefit, our fish will be in more capable hands and people will be more successful from the start. Right now too many people still view fish as "disposable" and too many people think this is something that can be accomplished without any level of knowledge from the start. That is so untrue. Anything living is going to require some kind of knowledge base to care for it or it dies. 1 + 1 = 2. If it eats it needs to be fed, if it is being fed it produces waste, if it produces waste it needs to be cleaned. This is the one thing I have noticed is missing in the many people who come to me asking for help. I don't wish to insult anyone, but I have found myself asking 1 question over and over during the many years I've been in this industry: Where is the common sense? I see this everywhere, and while I won't ever name anyone in particular, my years spent at the pet store overwhelmed me with the lack of common sense I saw in our customers. Next to that, simple ignorance was the next biggest issue. We had science teachers flood our fishroom every fall, and the number of them who gave us baffled looks when we mentioned the nitrogen cycle and water quality, and the number of them who answered with "huh?" when we asked how often they did water exchanges... it was sickening. I used to wonder at some of these people... some were college science professors, some were high school teachers... and these are the people educating my kids?? Why are our children not learning about the nitrogen cycle in school? They study everything else, but forget the basics?? Because this sort of thing is left out, forgotten, brushed under the rug... the general population never thinks about it, most don't know about it, and yet expect to mimic it at home? This is no more a "hobby" than keeping a dog or cat is a "hobby", and I think it's the responsibility of all concerned to fix the real problem. It is a customer's responsibility to ask the questions, it's the store's/supplier's responsibility to know the answers and provide them. It is also the store's supplier's responsibility to ask questions and to do research when needed. So much information is out there, but it's so scattered and difficult to find, that it's useless to most. It's also the responsibility of those who already have the answers to help teach it to others, even if it's just your children... teach SOMEONE, and keep the chain going. Fish keeping is not a "hobby", it's a responsibility.
Sometimes I think too much, lol. I didn't mean to overwhelm anyone... sorry to all for that. I guess it shows that I'm passionate about my work and about the animals. 
