Take a sample home and put lemon juice on it. What you will find is that the etches on dark marble show up white. Not at all attractive. And that's why only the white marbles are truly popular for kitchen counters. They show etches much less than the dark ones. Possibly use it as a vertical accent somewhere in your home (NOT a shower), but I wouldn't use it on any horizontal surface. Maybe a gorgeous full height backsplash where you have no uppers on a wall....or in an entry way directly facing you as a focal point. Think of it as art, not a work surface.

In all these examples, the breakfast counter separates the kitchen from the dining/living area, and is higher than the rest of the kitchen counter, to give some privacy to the chef and hide the mess of food preparation from guests

The wall is stunning and creative, but sadly, I have to agree with the consensus expressed on all your threads: this wood should have been bone dry, carefully checked over piece by piece for holes, insects, existing fungus etc., and probably treated and certainly well sealed before before being installed. At this point, I would cut my losses and take it down. Once the pieces are all down, it's possible that if you thoroughly scrub off all fungus with a bleach solution, then let them dry bone dry (preferably in a wood kiln or perhaps a DIY drying shed), then treat and coat, these pieces could be reinstalled. Even that depends on the conditions they'll see - if this wall is exposed to lots of steam or grease you'll be having new issues before long. Also, is the wall itself dry and solid? Any chance water is leaking or oozing from somewhere and adding to the issue? What species of wood is this? Some species are naturally more fungus resistant and appropriate for this than others. Long story short, I'd recommend finding a different way to cover the wall - with ceramic, galvanized metal, or with a really scrub-resistant paint.

quartz is a man made product using natural stone and a resin material. No sealing and is stain proof. I have had my granite for 10 years. I have never had a staining issue and set hot pots down on it seldom, but it has never bothered it. I've sealed it maybe 2-3 times over 10 years. granite really doesn't stain. So, compared to quartz, they are very similar. It all comes down to what you like the best.