Cheers mate, so I actually moved it into the existing topic. Threadomancy is much better than having multiple topics about the same issue. And April is not even that long ago…
On the question, there are no news! Someone recently entered a Chaos Dwarf army in a tournament and the Sorc had multiple Stone Mantles, but we don’t know how the Initiative issue was handled or if it was even discovered. Just by virtue of stacking multiple mantles on the same character: Yes, it’s an extremely common item, meaning you can have multiple ones within the same army or even equipped to the same character and/or combine with another item from the same category. But it is unclear how the -1 to initiative is handled and if maybe that excludes stacking multiple mantles of stone as those would bring you down to I0 or lower.