I checked where I got this information from, and yes, it was just a speculation. Other halfs surely can be stackable, I2C bus allows this and power pins can just be forwarded, but it would need every OtherHalf to have necessary connectors on their back side. Maybe just a few OtherHalfs, like an Extra Battery OtherHalf would implement that.

Thats why I think the qwerty-Otherhalf could have an extra battery integrated from the beginning. Besides, stacking Otherhalfs, although it would be technically possible, would make the device unpractically thick.

I also think the Otherhalf concept is not really as useful as some ppl think, because ppl will carry just one Otherhalf with them daily. So if Otherhalfs do not have multiple features combined, the idea is not as productive and luring as one may think.