Fairly extensively discussed, actually. Anyone can write in their own tongue, though the problem will be limited understanding by the readers who don't read that language...and then there's the danger of a writing becoming National/regional. Plus, as others have noted, there's us ignorant English-only readers (have mercy on us). English has been sorta accepted as the common tongue...though, again, that shouldn't stop someone...it would just take someone interpreting. (And I tried the interpreter, but the device is very literal, so the subtle meanings are lost...)

"Once in awhile we get shown the light, in the strangest of places, if we look at it right" - Hunter/Garcia