The original comment missed the point of the chart in the article you link: the increased pixel density is useless __at TV viewing distances__. When you go down to about 2 feet from the screen, 4k is pretty apparent on a 30 inch screen.

A clearer chart is at [1], and the Carlton Bale's original article even has a handy calculator that lets you verify this [2].

1: http://s3.carltonbale.com/resolution_chart.html 2: http://carltonbale.com/does-4k-resolution-matter/