The recent proposals to conserve or reject dinoflagellate names are commented. The Nomenclatural Committee for Algae (NCA) recommended to conserve Scrippsiella against Heteraulacus and Goniodoma (proposal #2382). The synonymy of Peridinium acuminatum and Glenodinium trochoideum is highly questionable, and one Steins illustration of Goniodoma acuminatum as type will solve the doubts. An alternative genus and family name for the gonyaulacoid taxa formerly classified in Goniodoma is not provided, and Scrippsiella is a junior synonym of Duboscquodinium. The NCA confirmed Amphidoma acuminata as type species against A. nucula (2577). Stein established Amphidoma nucula as the representative species of the genus, and the poor-defined A. acuminata is associated with higher nomenclatural instability because it is probably a Centrodinium species. The NCA recommended Heterocapsa steinii as type of Heterocapsa (2607). That species name is a junior synonym of Properidinium heterocapsum and Peridinium monas. That taxon and allied species should be placed in Cachonina because Stein proposed Heterocapsa for three species of the Kryptoperidiniaceae. The proposal to conserve Alexandrium against Blepharocysta (2686) is based on that Peridinium splendor-maris is a senior synonym of Alexandrium balechii, currently classified in Gessnerium. Peridinium splendor-maris is a collective name that includes undefined organisms, and no description or illustration corresponded to Alexandrium or Gessnerium. The NCA reported that Alexandrium catenella and A. fundyensis are synonyms, without comments on A. pacificum (2302). The consequence is that one of the five species of that group has not name. Naming taxa should follow the principle of priority and the article 7.3 of the International Code of Nomenclature for algae, fungi, and plants, and rejection or conservation of names should be exceptional. Based on a supposed nomenclatural stability, the NCA is creating arbitrariness and instability in naming dinoflagellate taxa based on questionable taxonomical interpretations.