I assume that you're referring to some of the DB members' use of Japanese move names in older moveset threads, like Klinklang's here? If so, this is because those movesets were posted in 2010, the year before the release of Pokemon Black and White in western countries. The games had already been released in Japan, but the English names of all the new Pokemon, abilities and moves were unknown at the time. In order to share and discuss strategy for Pokemon Black and White, we had to use the translated names of the moves.
Otherwise, the reason the Japanese names are used is that the Pokemon, move or ability was recently revealed in Japan but hasn't been announced elsewhere, and consequentially, only the Japanese names are known. A good example of this is the recent international reveal of Komala and Rockruff; Japanese magazine CoroCoro revealed them some weeks prior to the Pokemon Company, but we knew them only as "Nekkoara" and "Iwanko" at the time.