A wall under 0,8 millimeters (with casting and lost wax) can't be 3D printed without risk of breaking.
Online 3D printers refuse under this limit.
For jewellery, casting is better than sintering for a soft rendering.
My local caster who works for jewellery gave me the same limits (0,8 mm).
I have to take care this limits with my creations.
I think sintering have bigger limits with 1 mm minimal limit.