Q:

Handling coherent answers that aren't valid for the site

Over at Physics SE someone posted the following answer to the question "Can one create mass from energy?":

Yes. Genesis 2:7 "and Jehovah God went on to form the man out of dust". (God created man from dust.)
Genesis 2:19 "Now Jehovah God had been forming from the ground every wild animal of the field" (God created animals from ground)
However, in Genesis 1:1 "in the begining" God created the heavens & earth. (Here it didnt mention any preexistent materials used to built heavens & earth. So what did he used?)
Isaiah 40:26 "Because of his vast dynamic energy and his awe-inspiring power" God used energy/power to create heavens & earth (mass)
So Yes, Jehovah God can create mass from energy. NB: Scriptures are from the New World Translation of the Holy Scriptures

Not to pick on religion; I'm just taking this as an example of an answer that is utterly unrelated to the topic of the Q&A site it's posted on, and yet doesn't really meet the criteria for any of the standard flags.

It does straightforwardly answer the question and thus isn't suitable for a not-an-answer flag.
It is perfectly legible and coherent, thus doesn't fit the criteria for a low-quality flag.
It's not advertising or promoting anything, so isn't spam
It isn't rude and doesn't offend anyone

How should this answer be dealt with?
From the perspective of a non-mod: use a custom flag? Or should one of the standard flags be appropriate?
From the perspective of a mod: should be be deleted?
Yes, one might argue I should ask this on Physics Meta, but we're in the middle of reviewing our flag usage guidelines and I would like to get insight on how people on other sites would go about it.

A:

I would flag this Not An Answer or Very Low Quality, since it doesn't answer the question within the defined territory of the site topic. Not that the answer can be defined as 'low quality' in the sense of gibberish, it is a readable answer, but it is not salvageable through edits.
I don't doubt the good intentions of the (unregistered) new user, but the answer is useless on your site. There is no need to involve moderators here, users can vote to delete this item through the intended review queue.

