After the paper "A dry polishing technique for the petrographic examination of mudrocks" by Gorbanenko (2017), it is important to stress some differences between the proposed polishing procedure and the existing standards for sample preparation for microscopic examination of organic matter, which may lead to less bright surfaces than required for measuring vitrinite reflectance by the most widely used standards (7404-5 ISO, 2009 or ASTM D7708, 2014).