They're perfectly consistent, if it's legal and doesn't have the potential to harm, they'll keep it. If isn't legal and/or has the potential to harm, they won't.It's really funny to me that things like a single frame of animation get cut by the BBFC, but say...the entire Karen toothbrush scene in Nisemonogatari, and the Shinobu bath scene in Nisemonogatari went completely uncut. When MVM announced the release of Nisemonogatari a few years ago I was genuinely concerned that it would be cut. They're not very consistent are they? :-D
Of course potential to harm is subjective, but it generally refers to use/discussion of particular suicide techniques and very few animes actually get cut on those grounds.