I should be able to completely turn off comments in my Space

(User Story, To be Fixed , Priority: Critical, Test Status: No automated tests yet , Reported By Bad Link: Thing 3y285jl not found, )
Summary: We can mostly fake this with permissions, but what Anna wants for the Arisia Space is to completely disable Comments.
This should probably be a flag, which can be set on Space, Model or Thing. If present, it disables Comments completely at that level. Shouldn't be too hard to implement.