Any ship traveling towards another ship would have its nose pointed towards it.
If both ships travel towards each other, their noses would be aligned, but their roll would likely be different.
That's a bit different from what's being shown in the comic where ships seem to have any orientation, no matter the context.
As for a galactic up/down, the galactic disc would be the obvious reference. That still leaves a 50/50 chance that two civilizations would choose the same direction as up.
There is direction in space. Space is not a formless void there is order and structure to the universe.
The solar system is shaped like a disk. Most planets orbit and revolve to the same axis as the solar system.
When a star trek ship is seen in orbit, like the opening to TOS it is usually shown orbiting with the up of the ship facing the north of the planet, making a left turn with the planet off the port side.
Having a consistent orientation, like up=north would make sense for navigating a solar system. Federation ships in orbit are always shown rotating to face the direction of travel while in orbit. That's not at all needed to remain in orbit, but having consistent orientation seems important to the federation.
I'd like to think that it is an unspoken rule among all spacefaring people, regardless of their planetary origin or biological design, to automatically reorient their ships to match the "up" direction of any other ship they are approaching.
It makes sense since (effectively) all spacefaring peoples started on a planet with gravity and well defined "up" directions. You wouldn't interact with anyone in gravity while upside down, so as a courtesy you'd always want to be facing "up" for both your sake's.
Can't tell if this comic just doesn't get it or put zero thought into it. And there is several examples throughout the various series where two ships don't align to each other.
There are several reasons why the ships would always face each other, from common courtesy to defensive posturing.
When two ships face each other its like an nonverbal way of saying "we see you" or "you have our attention". Orientation also plays apart in this. Of course there is no real reason to orient so both ships face "up" thanks to artificial gravity, but it's also something that could be seen as polite and etiquette as getting on the same level as the other meeting them half way.
For defensive purposes, it also makes sense to nose towards a potential threat or adversary as within star trek the shields are strongest at the front (thanks to deflectors and navigational shielding) as well as the best/most accurate sensors to get a good reading. Additionally the forward arc of the ship will likely have the most overlapping weapon arcs, especially for ships like klingon bird of preys with fixed disruptor cannons facing forwards. This posture also tends to keep primary engineering, where the reactor/warp core is situated, obscured and defended, so if the ship wants to make a swift retreat their primary means of doing so is less likely to be damaged or disabled, and if you engage an FTL retreat towards a foes rear that foe needs to turn about and reorient themsevles to give chase, giving more time for the retreating party to take evasive action and avoid further intercepts.
There is a federation standard for which way is "up" based on the plane of the galaxy.
So at least that explains why Federation ships always meet on "level ground"
as for why the romulans, klingon, and various other non federation, especially non friendly species from the other quadrants, would be oriented the same way?
Idk, maybe the progenitor race from that one single episode of tng that never showed up or was spoken of again made some kind of subliminal or genetic memories of which way up should be.
Hilariously, they address this in the first season of Discovery.
When Starfleet ships meet with Klingon ships you see them out the windows hanging at odd angles. When two Starfleet ships meet, they warp in at an odd angle then bank and roll to align the ships to each other.
This reminds me of how in a lot of sci-fi universes, every planet the characters go down to has earth standard gravity. When in reality there would be a ton of variance, some planets would have 20% stronger, or weaker, or crushing.
Expeditionary Force book series was a breath of fresh air, portray space battles how they probably would play out, at such long ranges you could move your ship and avoid a directed energy weapon. The books also do a great job with there being more variety in planetary conditions too. I loved that series. The audio books are fantastic, R.C. Bray does a wonderful job!
Here's my retcon. The science of inertial dampeners are such that you have to be precisely aligned perpendicular to galactic north for maximum effectiveness.
When I run into other ships in space games I usually orient myself to be head on with them. Unless I'm trying to murder them, then I try to go wherever their guns aren't. Maybe Star Trek just skips showing that part.