When do you use "anathema" vs. "an anathema"?

According to this source:

“The word anathema can be used as a regular noun (essentially meaning “a thing cursed”) and a determiner can appear in front of it, “an anathema.” However, it is usually used as what Burchfield calls a “pseudo-adjective” or a predicate nominative (no determiner): “The union was anathema to the middle management class.”

Authority: The New Fowler’s Modern English Usage edited by R.W. Burchfield. Clarendon Press: Oxford, England. 1996. Used with the permission of Oxford University Press.”

So it’s just kind of… willy-nilly?

“An anathema” is both awkward and less common, so I use it without the indefinite article. But either usage is defensible.

Harp’s finding is in full accord with the educated use of it that I have seen in my own reading. I have never seen “an anathema” in stylistically respectable text.

“An anathema” makes one sound as if one is stuttering so one should avoid it at all costs.

I prefer to use it as a predicate nominative because it sounds more elegant. It makes me seem smarter than I actually am.

Thank goodness all you wordies have said so. I too never use it as a noun with an in front of it. It would be anathema to me.

There is a possibility of the word ananathema, meaning without anathema or revile.
“His objective is to be ananathema to mankind.”, which is not to say “he” wishes to be a positive force of good.