Statistical errors in equivalent widths -- A clarification

In a recent mathematical approach, Netzel (2018) proposes a method for determining the statistical error of spectral line equivalent widths. Using various approximations, he derives a determination equation that differs significantly from earlier approaches by Vollmann & Eversberg (2006) and Chalabaev & Mailard (1983) and evaluates these works with his approach. Several points stand out, which have a not to be neglected influence on the evaluation of this approach.