Nigh—Kinda, Sorta, Almost, Maybe, But Not Quite—Invulnerable

It is the ongoing curse of the Wonder Woman fan, the tendency for there to be a large discrepancy between what Wonder Woman is supposed to be and what we often get.
For all I’ve rambled on about Wonder Woman’s characterization and her portrayal, there’s no denying another significant issue that tends to plague her: her powers.

When Wonder Woman was first created way back when, Marston intended her to be a character “with all the strength of Superman.”

Of course, it's worth noting this was during a time when Superman’s powers weren’t exactly defined and he was pretty much a walking deus ex machina. People who watch Superman II today might tilt their head when he starts teleporting, shooting beams from his hand, levitating things, and wiping Lois’ memories with a kiss—but that was pretty much how Supes rolled when he was first created.
No joke, he once had the power to shoot a miniature version of himself out of his hand.

So even though Wonder Woman was created to be Superman’s equal, that was kind of a vague and dubious ambition, and her power levels have fluctuated wildly since then depending on the story and the writer.
One thing that definitely didn’t help Wonder Woman was for a long time a lot of people based their view of her abilities on her portrayal in Superfriends where…well, let me put it this way: there was an episode where the bad guys defeated Wonder Woman by digging a six foot hole and tricking her into falling in. And that was it, she was helpless.
So, yeah…

Point is, Wonder Woman is supposed to be an upper echelon powerhouse character. She should be the “most powerful” woman the way Superman is the “most powerful” man. Apropos. How powerful is the “strongest” woman in relation to the “strongest” man—I am not touching that. That’s a can of worms that never ends well.
And really, does it even matter? According to DC, Wonder Woman is “second only to Superman.” But then you have Captain Marvel who is said to be Superman's equal—but Cap's as strong as Hercules, and Wonder Woman is stronger than Hercules, and that's not even factoring in the Martian Manhunter, and...now I've gone cross-eyed.
Seriously though, in the grand scheme of things, is being able to bench 10,000 tons, but not 10,100 tons really that huge a difference? They're all...up there. Any discussion beyond that is semantics.

Moving on to the real issue—while we can accept where Diana is supposed to be in strength, it's past that I find things get muddy. Specifically, her endurance and durability.
Common logic says that the rest of a character’s abilities kind-of, sort-of follow suit with their strength. Therefore how durable a character is should more or less be in proportion to how strong they are. And that’s where Wonder Woman comes into problems, because there tends to be a clash with a character who can go toe-to-toe with the likes of Superman, but can still be harmed or even killed by bullets, knives, and arrows.

There is something inherently ludicrous (and profoundly lame) that we have a Wonder Woman that can fight a raging goddess in a pool of lava...

...but still be knocked out by a pellet of sleeping gas:

I don't approve.

Some try to explain this using some pseudo-science about how Diana can withstand flat, surface blows—like a punch from Superman, or plowing through a mountain—but sharp, pointed objects like bullets and knives at high velocity can hurt her.
I don’t think you need to be an expert at physics to know that really doesn’t work—even with comic book logic.

One could make a case that, seeing as Wonder Woman’s powers are magical in nature, we shouldn’t bother trying to apply a “scientific” explanation and accept the limitation of Diana’s abilities to be the work of the gods. And while that reeks of the, “It’s magic, so we don’t have to explain it” cop-out, it isn't entirely unreasonable. After all, what was the scientific explanation for Achilles—a supreme, unstoppable, mega-bad ass—dying when someone shot his ankle?
One could find a bit of logic in the gods’ having motivation to limit Diana’s abilities. Perhaps their way of reminding her that, as powerful as she is, she is not invincible or unbeatable.

But if we’re to go that route, we should then define it. While there was nothing scientific about Achilles' weakness, it was explained in the myth. So did the gods decree, “And lo, Diana shall be highly resistant to unarmed combat & the elements, but not so much actual, man-made weaponry”?
That would be oddly particular of the gods.
But I think if one thinks about that for more than a minute they'll find a lot of holes. Not to mention it kind of suggests a two-bit thug armed with a knife poses a more physical threat to Wonder Woman than an unarmed Giganta.

Some might argue they should just go ahead and declare Wonder Woman’s powers include invulnerability.
Here’s the immediate problem with that: kind of undermines the bracelets. Sure, she could still find practical use—the bracelets do do more than just deflect bullets—but it does seem a shame to make it where Wonder Woman can say, “I can use the bracelets, but I don’t really need them.”

Another problem is this potentially puts her in a similar trap as Superman where she’ll come across as overpowered. And I'm inclined to agree—it's nice to see a character who has the strength to fight upper-class villains like Mongul or Darkseid, but still can be severely wounded.
I think most would agree on that, no?

Here’s the thing with the whole bullets issue I think a lot of people overlook or ignore: there are many different types of guns and bullets with a wide range of penetrating power. There are guns/bullets where, if you shot someone point blank, the bullet would not come out the other side. At the other end of the spectrum, there are guns & bullets specifically designed to rip through steel.
And then there’s distance the guns are being fired from. A low-powered gun fired from far away won’t do nearly as much damage as the same gun fired from a foot away.

So with that in mind, should we not consider that just maybe some bullets won’t harm Wonder Woman without her being officially designated “invulnerable”? Some might rip right through her, sure, but some might only break the skin. Some might leave little more than a bruise. And hell, maybe some shouldn’t even harm her at all and do little more damage than a BB gun.
That still facilitates the need for bracelets because from Diana’s perspective, why take the chance? And even if the weapon won’t kill her, why endure potential pain and injury?

The same should apply to knives, arrows, poisons, and anything else.
Can we not acknowledge that a massive, fuck-all sword, made from some super-duper adamantium-type of metal, wielded by a jacked-up demigod is not the same as a crack-head wielding his $6.00 pocket knife? That a standard, run-of-the-mill arrow shot by some dude isn’t the same as a special arrow blessed by gods or made by aliens? That only specially made, super-poisons that would instantly kill a normal person can slow Diana down, while regular ol' chloroform don't do jack?

With that in mind, does Wonder Woman’s ability to fight the likes of Superman and his others in his league, but still be wounded by gunfire and blades, make a little more sense?

It should, I would think, but unfortunately, this is where we can't have nice things:
I think for the most part, most fans—and probably writers as well—prefer when things are distilled into simple, black & white stats that are easily documented.

Compare with Superman. Invulnerability is listed as one of Superman’s abilities—even though he really isn’t. If he were really invulnerable, it wouldn’t mean a damn thing how strong Mongul is. But okay, he’s “invulnerable,” except for Kryptonite and magic. Clear, direct, and simple even if writers don't adhere to it exactly. And if/when they don't, fans have a clear, direct, go-to definition to justify their grievance.

Now Wonder Woman—look at all that stuff I wrote about different kinds of weapons should have different effects on her. Certain things she can withstand, some things she cannot. That’s ambiguous and open to interpretation. You could make a chart documenting exactly what kinds of weapons can harm her under what circumstances, but who the hell wants to deal with that?

On the one hand, that allows the writer a lot of room to work with. On the other hand, it opens the door to inconsistency.
And tragically for poor Wonder Woman, consistency has not been her friend.