Hi, good question, this deserves indeed explanation, we have set impact directions in "our" categories, and with these set, the direction of the flow in the category does not need to be considered in the factor, but only the amount (for an output category, such as climate change, flows on the input side always are deducted from the LCIA result, while outputs add to the result). This does not need to be reflected with a negative sign. A negative sign is only needed if a flow on the same side as the impact category reduces the impact. Note that this works in openLCA 2.0.3 only (and future versions).
We kept the ecoinvent methods untouched therefore they still need the negative sign.
I hope this was clear? Thank you and best wishes,
Andreas
edit: I was incorrect for carbon dioxide to soil, please see comments below