Pierangelo Masarati writes:

I don't know how useful it would be to have back-ldif directly implement compare, as soon as one only uses it for back-config and not for a real storage with stacked overlays (however I note that back-config needs at least to nicely interoperate with one overlay: slapo-syncprov).

Syncprov does use compare, and back-config doesn't provide it. I don't know if that's a problem.

I forgot, back-config doesn't fall back to back-ldif for reads. So I guess it's just as well to leave back-ldif as it is.