With the goal of being modular, I don't want anyone changing the ElementalDefs unless they are adding to it. The mods I make before release will of course be core mods, but I am not aiming to allow that kind of mod to work with anyone else's. I honestly don't even know all the changes I have made to the file. It would take some time to compare it to the backup copy.

Though I try very hard not to, it seems impossible to make any substantial mod without changing something in the core files or in the ElementalDefs.

Is it possible to put just the changed tags in the ElementalDefs file in the mods folder rather than putting the entire file?  I tried that once and I kept getting crashes though, admittedly, it might have been due to my changes.

Weird file. I tried a single external tag change and promptly crashed the game. So much for trying to control it. Carry on.