If I recall correctly there was a similar issue years ago pre-Danbooru with Berserk regarding Guts's name. Fansubbers used "Gatts" (Gattsu) because "Guts" sounds a little odd for a name, but it was later confirmed by the author that it was in fact supposed to be Guts.
... But then again, I've seen Griffith's name spelled (officially) as Griffiths in the menu of the R2 DVD release. The US version used Griffith IIRC. A little bit of an odd case as both are actual name spellings, and there is no hard ending "th" sound in Japanese. As far as I know the "Griffith" spelling is now considered the correct one. Danbooru uses it, at least.