Even civ ships are able to pass. Trying to trade but It doesn't seem to work. If that's the case It's 10 times harder to go tall with the Vaulters.

I think it's by design. Trading isn't their strong side. Maybe should have broght few Roving clans mebers aboard Argosy.

While it's unfortunate that isolated systems can't be linked to the trade network via portals, it sort of makes sence - trade value appears to be calculated based on the distance traveled between system via lanes. If the portals were counted as valid trade route options, all of the systems would be adjacent to each other, bringing trade profits to minimal values.