So like, trolls know their sign means void or light or stuff? Like "Oh yeah, man, I am an Aquaza, which means I am mind and Derse. Idk what Derse is, but apparently I am Derse."? They know this?

They have no way of knowing what ‘Derse’ is because no one is aware of SBURB in itself. Aspects are metaphysical parts of the Homestuck Universe, but again, it may be more in a zodiac kind of sense, and likely not even using the same terms for Aspects. You know the type like. “Oh, I’m a fire sign, that means I’m x and y” “I was born on April so X Y Z”. That kinda stuff is way more likely, specially given Trolls have kind of a thing for fated stuff and karma.

There’s also like a MILLION more Signs we haven’t seen. The Extended Zodiac is just for us the Audience to see some things more clearly.