I might have missed something, but I attempted to fill a report for the band Moreld, a Norwegian Black metal band with Christian lyrics to alter its genre-field to "Black" Metal, which is, as far as I know/knew is the usual thing to do. However, the report got closed by Azmodes with the rather laconic words: " We no longer use that terminology." I might have missed something out but why/how has this change been made? Sorry again if I missed a relevant thread.

As far as I know, that terminology was originally used as a compromise between people who wanted the Christian black metal bands to be labeled as "Unblack Metal" and people who didn't want there to be any change listed. Apparently the new consensus is that there isn't enough sonic distinction inherently associated with the Christian themes for the bands to be labeled as such.

And the lyrical themes already sort every christian band in the advanced search anyway.
As Hellhammer said "In my opinion, black metal today is just music"

It has been a point of contention, but it isn't encyclopedic to list the musical genre differently. We don't differentiate ideologies in musical genres.

Functionally, we use some sort of "black metal" to label a bunch of crying, screaming babies in Depressive Illusions and Self Mutilation Services emo bands as black metal, we label life-celebrating Christian music like Mortification as "death metal", and we label the limpest, most powerless flower metal like recent Sonata Arctica as "power metal" because those are functional descriptors of a style of music that effectively relay the style of music to the general public.

It isn't objective and encyclopedic to differentiate musical genres based on ideology, and it's impractical to draw a certain line on where we do so, so we don't.