Confused about the "Carbine" category
 

To my knowledge, the carbine classification is purely based on a firearm's barrel length, and has nothing whatsoever to do with a firearm's firing modes or caliber. You can have pistol-caliber carbines, assault rifle caliber carbines, battle rifle caliber carbines, etc. Is the classification then too inclusive?

Right now, I don't know about any "dedicated carbines" on the wiki other than the M1 Carbine, CX4 Storm, and De Lisle Carbine pages. The others are either older pre-20th century firearms or just carbine-length versions of assault rifles (such as the M16), battle rifles (such as the SCAR-H), or even pistol-caliber carbine versions of submachine guns (such as those for the HK MP5, IMI Uzi, or HK UMP).

If one of the current goals for this wiki is streamlining categories, then would it be simpler to just to note on the firearm's page that a firearm is a carbine instead of having a distinct category for it?

Carbine is such a loosely defined term it would be stupid to put it as a category. I say streamline the categories not make more.

Agreed. Carbine is another term that's too vague to deserve a category. I'd be fine ditching it.

All else...yay or nay?

Well, I hope then that all the "Dedicated Carbines" find their appropriate "parent firearm type" pages then.

Some examples, like the CX4, would be easy since the CX4 is a pistol-caliber carbine, not a submachine gun (though related to that class) by virtue of being semiautomatic-fire only. The M1 Carbine could be considered a prototypical assault-rifle since it uses an intermediate cartridge, but only the M2 version had select-fire capability, and its cartridge (the .30 Carbine) used pistol primer, which certainly seems underpowered for an assault rifle.

How about the De Lisle Carbine? Is it going to go under the submachine gun category as well since it could be argued that its of an integral suppressor makes it a bolt-action predecessor to the MP5SD series?

The De Lisle Carbine is obvously a rifle and should be classed as such. It's a bolt-action and is very obviously not full-auto.

The PX4 does have a 'de-sporterized' SMG variant now (MX4). We'll probably see some in films eventually, since they're so 'futuristic looking'. Classifying it is sort of the same situation as the HK94, but backwards.
The DeLisle was based on a SMLE, so I'd call it a rifle. Even if it fires .45ACP from a 1911 mag through a Tommy gun barrel.

You forgot to mention the Lee-Enfield stock. EDIT: oh, wait you did. Never mind

So we'll put the MX4 on the same page as the CX4 when it starts appearing in media, much like we have pistol-caliber carbines on the same pages as their parent firearms (such as the Uzi SMG and Uzi Carbine, the MP5 and HK94, and the UMP and UCP)?

It seems pretty rare that an SMG version of a pistol-caliber carbine is officially produced after the pistol caliber carbine is commercially available.

I wouldn't say obviously, it's more like a giant pistol with a stock and barrel extension since it still fires a pistol bullet. Though it's so much of a frankengun that if it had only appeared in a videogame rather than real life you'd probably have arguments about whether it should be on any pages at all.