@Muad'dib, I think it adds new words that do not exist in the DF languages yet.

The current version of DF refuses to load any mods that have duplicate objects. Language_sym.txt has two duplicate entries (words that already occur in the vanilla language). This causes worldgen to abort. You can delete the file entirely like you did, or just remove the two conflicting words from it. That way the other new words still show up.
The two duplicate words are DOMINION and EMPIRE. If those entries are removed from the file, it works again.

Alright so what seems to have worked for me was completely removing language_SYM.txt from the mod's object folder in the Appdata/Roaming files of the game. As for the toy scimitar it was because of another one of my mods (Dark Elves Redux).

Not sure if this is the same SYM file you were talking about earlier with another person. Does that SYM txt file do anything important?

Hm, I don't think it should cause any ingame problems, but still would try to figure it out

It looks like the latest update to the game might've messed with something in the mod. It was working well up until last week, now I get the following error messages in my error log.

Duplicate Object: item ITEM_TOY_SCIMITAR
Duplicate Object: word DOMINION
Duplicate Object: word EMPIRE

The scimitar may be connected to another mod that has toy scimitars, but I have not been able to find a work around. Any clues?

P.S: Awesome mod!

Yes, because only new civs use new languages. They would still use vanilla words, but that should not be a big problem.

I am really eager to try this mod, sounds very interesting. Is it compatible with the other major language overhaul mods?

This is not a playable faction (tho its easy to change that)

It's for adding different flavors for visitors, siedges and trade + map/history in general ofc

Is this more like a tailored human experience rather than a playable human faction enabler? I'm sorry for the stupid question, just trying to figure out what other mods would go good along this one.

Damn, that was me accidently coping a vanilla file into the mod folder. Deleted it now and uploaded an update!
Thanks for the investigation!

Deleting language_words.txt from the objects mods folder fixes most of those, the two remaining duplicates are newly added words from the language_sym file that already exist in the vanilla language. removing those fixes the last duplicates, but I'm not sure if those fixes have unintended consequences for the mod.

First, I really like the concept of this mod, and I've started a new game to test it.

There seems to be an error with the languages, somehow if I save and load several times with just this mod enabled, a long list of errors pops up in the errorlog.txt file, with duplicate_object errors, like:

Duplicate Object: word COMPANY
Duplicate Object: word FESTIVAL
etc.

This causes the names of objects and people in the game to break down. There's a couple of other errors in the errorlog that seem to have less impact.

I've gone down the DF material rabbithole and lost much sleep to the wiki and to the game's arena mode. I need to test things more (to make sure the metals are doing what the calculations say they should), but I'd love to send you my changes with notes. I'll do that in a sec, but bear in mind that it's not 100% tested.

Could I be wrong somewhere? No, no, surely not. Not I. Unless...

Yeah, it should! But I don't think that it would works as simple as that. You can't just make it heavier, it would get more dense so it would be even better at blunt damage. So it's easy to break things here, but if you would find a way I would deffo think about some changes!

Material physics is a delicate and confusing thing :)

I love the idea of adding more distinction to the civs! I've been messing with my own settings a lot to create a race with more size and physical strength, but limited to copper and bronze. I'm wanting to work this mod into my next world, but I'm a little concerned about giving a 'plain steel alternative' to humans (surely dwarves deserve a metallurgical advantage outside of craftsman quality), so I'm thinking I might make Black Steel heavier for both some advantages and disadvantages. Maybe making Damascus Steel slightly more brittle too. Would just editing the metal's properties itself accomplish that?

Such a fuego idea for flavor

sounds nice, i like the idea of expanding human factions so that they arent all mostly same

It shouldn't conflict with anything, it just adds two additional civ types. Everything inside is vanilla friendly and should be working correctly with most mods. 

I used it with a bunch of different mods in my current run, so far no problems

Does it conflict with anything vanilla? Do I have to disable anything to make the experience optimal?

Thanks! It's based upon biomes, not attitude so it should be fine :)

Sounds great, I'll add it to the next world I'm starting, likely when adventure mode goes out of beta. The use of dialects rather than completely new languages is a nice touch. Not sure about the North-South thing as my current world for example has the cold regions at the south end of the map.