We need to think carefully about the value, or not, of digging compost and charcoal into the soil to make a deep Terra preta type soil. I do like to bury large amounts of carbon deep in the soil for several reason including drainage and prevention of leaching. The charcoal, however is always put into the top 6 inches of soil. Moreover, this is usually an addition to planting holes especially the potatoes, peas, beans and sweet peas.
There is an alternative method which involves no digging and a raising of soil level by addition of compost and charcoal to the surface. One of the raised bed systems - although you could just raise the beds without the obligatory wooden edges if you wanted to.
These methods are not necessarily mutually exclusive.
While I have dug over parts of the allotment, I have not dug over other areas. In the no dig areas I have used home made compost and charcoal as a mulch. As the compost is a few years old, it just looks like good friable soil with a lot of carbon in it.
I can see there could be a conflict between the diggers and the non diggers where there does not need to be one.
Both methods are valuable depending on what you want to plant. I like to dig in lots of stable manure for my potatoes. The peas and French beans are just getting a 2-3 inch mulch of home made compost on top of the soil.
The root bed got home made compost dug in.
Maybe we should all be using mattock and have done with it