Hi Sacha,
Activated carbon helps to remove discoloration and other organic/inorganic toxins so it's benefits can be worth more than whatever trouble it causes. On the other hand, activated carbon is not a necessity either so if you remove it it not really a big deal. In other words, activated carbon won't make or break your tank so there is really no need to fret about it one way or the other.
Here in JamesC's post is a summary of the bad things that a fresh set of activated carbon removes from the water column:
Does carbon remove trace elements? | UK Aquatic Plant Society
Look in the paragraph labeled High to very good adsorption. Do you see any nasties in that group?. Just about all of them right? Well, those are the things that activated carbon is really good at removing.
Then there is the fact that activated carbon has some of the highest surface area per unit mass - even higher than the atrociously high priced filter media. Therefore it attracts and build nitrifying bacterial colonies in exactly the same way as any other filter media. So even though there is an end to the chemical adsorption after a while, the carbon then behaves as a high surface area biomedia. It never needs to be replaced unless you want to continue to use the adsorption feature.
Activation of carbon is accomplished using high temperature steam often in excess of 1000 deg.C or with other gasses such as CO2 or Oxygen, which essentially bores out tiny holes within the charcoal structure. This greatly increases the number of adsorption sites per unit volume. Charcoal activated in this manner will have anywhere from 500-1500 square meters per gram of material of adsorption area. Activation can also be accomplished using chemical means, such as with strong acids.
You can even use the bio-media feature as a substrate. Carbon works fine as a substrate, although it is a bit light and it may not look good. You can mix it in with other materials to bulk it up and the carbon will develop bacterial colonies there like any other sediment.
When starting up a tank a really good thing to use is a combination of carbon and zeolite, which is a mineral that has a strong attraction to ammonia and that will help control ammonia an other toxic compounds in the sediment.
I mean, there are no bad reasons for using activated carbon. All of these supposedly bad reasons boil down to the fact that a minor amount of Iron is pulled from the water column. Carbon haters always talk about that, but as I mentioned, you can just add more Fe and get on with it.
Cheers,