The main issue to me about this, is the degree of permitting questions whose only tie to the game is a mere "Is this confirmed or addressed at all in the canon?". If it fits within the logical or canonical context of the story or its setting, it can be a very sensible question.
But there has to be a limit, some kind of threshold, to what kind of tie it must have. Take the following question.
"Why does Aperture Science use storage cubes instead of hexagonal prisms?"
It sounds quite silly, doesn't it? It's sufficiently outside the realm and context of the story that it's not reasonably answerable by gamers.
If we instead take it as...
"Does the canon of Portal address why Aperture Science doesn't use storage hexagons?"
...then does it sound any less silly as a question?
We allow plot questions because we have canon to address it. We don't accept extracanonical questions because we have no material to use. We accept questions that ask about things that may not be touched on by the story directly, generally under the assumption that there is a very reasonable tie between the material of the question and the material of the canon.
I'm personally not familiar with Portal canon, so the following is based only on how I know bits and pieces of it. From what I know, the applications of energy consumption are never discussed, nor are some of the other uses of portals. For example, terminal velocity could be abused to develop high-velocity weaponry. Or, attaching a portal to a remotely controlled surface as a dual-purpose espionage/infiltration system. There's a lot of possible applications of Portals, that's one of the wonderful things. But nigh all of them are ever in the context of the backstory. As such, to me, the question is barely tied to the context, and only beats the hexagon question in terms of not being quite as silly.
I was once discussing with another moderator of another site about a theoretical "No one cares" close reason. I didn't really support it, on the bounds that Not A Real Question generally covers it, as does the new and improved Too Localized:
This question is unlikely to ever help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet.
As such, I feel that the ties to the context of the story or game figure heavily into the scope of who actually is interested in such plot questions. I am willing to be corrected about the ties of this particular question to the context of Portal, and will support its reopening in that scenario. But I feel that more importantly, we shouldn't simply allow a question and disregard the context just because we can answer it.