The Core is Down
The Core is a place of mystery and shifting definition. What is true one moment may be completely false the next and few people agree on the metaphysics of the place. Nevertheless, there is one consistent fact. The Core is always Down.
This doesn't mean Down as in the Earth's core, nor in a way that is oriented to any specific planet or universe. The Core is below those who wish to enter it, at the feet of anyone driven to explore what lies beneath.
Entrances to the Core tend to manifest differently for everyone. Some people might find an elevator with just one button marked as -0, others might find a cavernous tunnel leading into the gloomy depths. Others still might simply fall asleep and wake up in the Core.
⏬ is a symbol used by the community to indicate general positivity. It tends to stand for "I'm Down for this", with the sense of doubling down on an idea. The double down arrow is often used in iconography and as a shape-basis for logos.
⚙️ is more commonly seen due to confusion over what the down arrow was meant to represent. It is usually interpreted as "gearing up" or "shifting gears".