The use of DNA has helped to improve and speed up species identification and delimitation. However, it also provides new challenges to taxonomists. Incongruence of outcome from various markers and delimitation methods, bias from sampling and skewed species distribution, implemented models, and the choice of methods/ priors may mislead results and also may, in conclusion, increase elements of subjectivity in species taxonomy. Lack of direct diagnostic outcome from most contemporary molecular delimitation approaches and need of reference to existing and best sampled trait reference systems, reveals the need of refining criteria of species diagnosis and diagnosability in the current framework of nomenclature codes and good practices to avoid nomenclatorial instability, parallel taxonomies, and consequently more and new taxonomic impediment.