ok my question is in wing commander is interstellar communication limited to the speed of travel and therefore relies on couriers, or is there a form of FTL radio in use and couriers are just for sensitive stuff?
In the interests of scale, in the WC4 manual's introduction that was taken from the "upcoming" novel, Blair commented to himself that the Confed Senate news vid had made it to Nephele in just a few days, rather than the weeks it normally took to get anything from Earth, so "it must be hot".
Certainly military and political channels take priority in the bandwidth of the comm relays. It might even be that the average folks' personal comms get assessed a "long distance" or "postage rate" fee based on how fast you want it some place. Even then, you have to figure that the capabilities of a jump node relay are limited to Tachyon speeds at best.
Light travels from Neptune to Earth in about 4 hours or so. So if you imagine that a system has a com relay at a jump point, but the jump points in the system are all in their different orbits, the distance between a pair of points can vary considerably and increase or decrease the time a signal takes to travel across a system. Imagine Sol has a pair of jump points at perfect opposite ends of Neptune's orbit. You're looking at a through-system time of more than eight hours at the speed of light. Now add this up over several systems worth of jumps and space and you get a lot of lag being created. Now add in a priority level to the packet information being sent.
Sorry to say it folks, but Dark Helmet said it best: "Even in the future nothing works!"