The sectional name cannot be a synonym of the species name!
Mycena corticola (Pers.) Gray
Preferred Synonyms:Mycena sect. Supinae
However, M. meliigena isn’t the only species that has gone under Mycena corticola sensu [author]. M. corticalis, M. pseudocorticola and M. supina are also likely misidentified as M. corticola here as well, so I think it would be best to have it deprecated to the section all of these species are in.
Maas Geesteranus, R. A. 1979. Three Mycenas revised. Persoonia 10(2): 277-282.
Maas Geesteranus, R. A. 1992. Mycenas of the northern hemisphere II. Conspectus of the Mycenas of the northern hemisphere. Koninklijke Nederlandse Akademie van Weteschappen, Amsterdam, the Netherlands. 494 p.
M. meliigena is the correct name for M. corticola sensu everyone.