Hey #linux people, weird question:

How much would I subtly break my system by having one Arch based distro and one Debian based distro both sharing a common /home partition? 

@tek_dmn
Well Arch is involved, so there is going to be at least twice the breakage you’d expect. 
@tek_dmn your ~/.config would probably break things a bit, but if you run the same DE on both it should be fine?
@tek_dmn depends how mismatched your versioning is. I would recommend having a separate data folder/partition than ~home if you can
@tek_dmn It's probably mostly fine. I have a zpool for `/home` that is shared between Chimera Linux and Arch Linux installs on the same machine (I.e. very different linuxes). The only thing that has been an issue is Firefox if the versions get mismatched. The system with the older Firefox version won't open a profile last used by the newer one. I Fixed this by creating separate arch and chimera Firefox profiles (`firefox --ProfileManager`).
@tek_dmn
I'd say very much. Older software will break trying to load config or data touched by newer version.
@tek_dmn
It really depends on how much version mismatch between applications installed on both systems there is and how well those applications handle the mismatch. Of course, with a bleeding edge distro like Arch involved, my best advice would be to expect surprises.