Tā zhè rén jiǎnzhí shì ge méixīngchèng, shuōhuà bànshì bùzhī qīngzhòng.
He's a complete no-marks scale; he has no sense of proportion in what he says or does.
Tips
memory
A traditional steelyard has notches (星) that mark the weight. A scale 没星 has no markings, so it can't tell light from heavy: a perfect metaphor for someone with no sense of what matters.
