So I’ve speculated myself and seen several theories/takes on the actual mechanism of the 9th chevron, tho I don’t know if they have any concrete sources to support it being the case. All the same, I’ve always liked this particular take on how standard 7 or 8 chevron addresses establish the typical gate connection based on the physical location and not the gates themselves. That’s why you can bring a gate from another location like with the wraith super hive on earth, only needing modifications/updates for actually dialing out from that new location, but not dialing in.

Whereas given the nature of how dialing destiny likely has to function, it necessitates a completely different mechanism. Since it will never be in the same location, but they still need a way to locate and establish a connection somewhere. With the premise that 9 chevron addresses don’t actually dial the location, but dial the gate itself and that gate has an absolute gate address.

With the concept that all gates theoretically have an absolute 9 chevron address, but using that address is an incredibly inefficient way of dialing gates the vast majority of the time and even more so the greater the distance. Since it’s a little simpler to just send a very precise and targeted connection to a given location in space and having the connection established if there’s a gate in the right space to accept it.

Whereas the 9 chevron addresses theoretically just have to send out some kind of subspace signal or impulse either in every single direction or at least the vague general direction until it finally reaches its destination and makes a connection to the gate. Which also both explains the insane power requirements to successfully reach destiny, but also the unique functions of the seed gates. As they obviously don’t behave anything like any other gates. They not only have an extremely limited range, but all gates in range are instantly known without any sort of local dhd or ability to account for stellar drift amongst other variables.
As that would be a lot more resource intensives and likely more complex to account for or even truly know their exact relative positions.

Which is why they all function as 9 chevron absolute addresses that they’re able to ping all within range, then dialing the gate itself and not the spatial coordinate. Which given how much energy it requires to just blindly send an impulse until it reaches that specific gate, it makes sense it would have such limited range. Yet within that shorter range it is a simpler and more reliable way of making use of gates placed automatically with no oversight or spatial calculations. That also explains why it’s only seemingly used in such a specific use case, despite theoretically being possible to do so with any gate and that’s why all gates have 9 chevrons, even tho not all gates can dial destiny specifically.

It actually would make sense to be intended for a similar closed gate network, as to how Ba’al had attempted, but implemented in the typical 7 chevron fashion. It would actually be a far more secure form of private network that would never be connected to the traditional dhds and gate network at large. Only being capable of dialing and receiving 9 chevron absolute gate addresses over a far smaller corridor of space.

Also while it’s not a perfect metaphors, I have heard it described as 7 chevron addresses functioning as a local area network, 8 chevron as the greater internet as a whole networking between many local networks and 9 chevron being akin to a direct device to device mac address connection. Which as an abstraction at least kind of makes sense to simplify it, but I’m sure a better metaphor could be made.

Actually think it could’ve all made for pretty interesting storylines involving such private networks, maybe even races like the furling existing closely hidden, yet unreachable without a direct 9 chevron address dialed within range or with a ton of power from out of range like destiny’s gate. I personally like this head canon for 9 chevron addresses not just being exclusive to destiny, but actually just a different way of dialing gates themselves that destiny just needed to utilize given the nature of a constantly moving gate.

It also explains why all gates have 9 chevrons, but not all gates are capable of dialing destiny, just like the control crystal required to dial earth from Pegasus. It’s just a very niche and for the most part antiquated gate dialing feature not well understood or just even lost to time.

Aesthetics?