Hello guys,
new guy here (for posting, have been reading the forums quite a bit though and got kinda stuck in the rules-section ^^).
Now, the last post here is a few weeks old but my guess is, that this issue hasn't been resolved yet, so here is my take:
While I do see the "Treating '-' as '0' seems legit, but we don't actually know"-point of view, I don't think it's actually valid and the solution is in fact completly covered by the rules, so I am with Godlyness on this one and here's why:
First we look at the definition of '-' as a stat and we will see, that it is defined as "Model doesn't posess the stat" and thus "can't be modified". Cool. What does this actually imply though? A missing stat doesn't mean it equals "0". It also doesn't mean it equals "infinity" or "13" or "we don't know what it is". It means just what the book says: the stat isn't there. What are the consequences of a missing stat? There are obvious ones, like a missing "cg"-stat meaning the creature can't charge, missing "wk" meaning the creature can't walk and so on. Are there other consequences though? None that are covered by rules at this point at least so we'll go with that.
Now we are prompted to make a simple duel. But can we even take that simple duel with the corresponding stat missing? Sure we can, possessing a certain stat is no requirement here and there is nothing in the rules that prevents the duel from occuring. So again we look at the rules and follow the instructions given there. The important bit here is obviously the "flip a card and add stat"-part. So we do just that. We flip a card and add the stat. Our model has a value '-' which by definition means it doesn't posess it and thus can't add the stat to the value-total. Not adding a stat (because we can't due to our stat in question missing) is equivalent to adding "0". Note though, that it is not the "same" thing as having a value of '0', only that not adding anything is equivalent to adding '0', which is a fine differentiation sure, but one that keeps us within the current rules-set without making any assumptions like '-' = '0'.
I think with that, the course of action which already seemed like the most reasonable or prefered one to most people is actually the one that's indeed completly covered in the current rule-set.
Naturally I am not without flaws so if I missed something or my logic is flawed at some point be sure to call me out on that!
Regards,
Snickch