User blog comment:FallenShadow/Fallen's Reviews: Chapter 341-343/@comment-7418318-20130711173547/@comment-4933386-20130712115529

There's probably some other uses of the Eternal Flame that we don't know...

aand I think Natsu may not eat the Eternal Flame... as he is already extremely powerful after Second Origin Release. Having Eternal Flame would probably make him literally indestructable.