Earlier quoted context omitted.
I guess that concise implementations (e.g. in a one liner) are often a complete bitch to debug when someone else comes back to it to fix a problem years later. It is much more difficult to debug and fix existing code than develop it from scratch. Hence, if you found the problem hard to code in the first place, then when you come to debug it again later you've just screwed your future self.
The problem with people writing too concise code is with their motivation not with their abilities - and so it is probably impossible to test (at least directly), because on the test they would have the motivation to do the right thing.
No. If someone has to be "motivated" to write clear code, especially given that these tests are supposed to lead to jobs, then I would have to question their abilities. Writing clear code is an ability of itself.