[gspencley]

I don't think that amluto is saying that the hardwood itself is inappropriate, or is necessarily ever inappropriate. I think they are saying that the specific joinery in their example was form over function, to the point where the joint was a critical point of failure.

Having done a bit of woodworking as a hobby, I would say that hardwood could be inappropriate if it is used for an element that is purely structural, internal (and thus will be hidden by external features) and there are cheaper alternatives that are just as good, or stronger materials available and we are talking about a critical structural element.

That's a pretty abstract answer but it's always going to depend on the specific project. Sometimes a piece of furniture has no hidden internal structure, or the appeal of the furniture is that it is all bare wood and you want it made entirely out of a beautiful "furniture grade" hardwood. For certain upholstered furniture, such as many sofas, using expensive materials for inner framing could not only be superfluous and add unnecessary cost to the piece, but in certain circumstances there may be better materials available even if you could make a perfectly adequate structural support that will last a lifetime using expensive hardwood and the right joinery for critical stress points.

I read amulto's point as being "expensive material and fancy joinery doesn't matter if you have a weak design."