reiyasona said:
However, a trained eye can very well spot huge differences by looking at the armament, armor and overall construction.
I consider myself to have a reasonably "trained eye", as you say, but I would be hard-pressed to spot many huge differences between an M26 Pershing medium tank and the exact same M26 Pershing heavy tank after the type's reclassification. Nor, from the right side, between an M2A2 infantry fighting vehicle, M3A2 armored reconnaissance vehicle, and M6 self-propelled air defense vehicle. I could, however, very easily list some huge differences between the Aufklfz 93, BRM-3K, and AMX-10 RC armored reconnaissance vehicles. (Like the conspicuous lack of a huge gun on the Auflkfz 93.) Or between the Kornet-D, M50 Ontos, and Kanonjagdpanzer tank destroyers.
Not every vehicle depicted by an artist corresponds to a real-world type, is drawn in great detail, or is clearly depicted. Nonetheless, tanks still tend to look like tanks (i.e. there's a sort of archetype for "what tanks look like"), and so we can tag them as such. This is not the case with a great many more-specific classifications. "what tank destroyers look like" is meaningless, because nothing looks like a generic tank destroyer. With the huge variety of tank destroyers in existence, any given vehicle resembles, at best, some subset of tank destroyers. The same problem exists, albeit to a lesser extent, with subclasses of tank. An M2A1 light tank looks quite different from an M551, and a T2 medium tank quite different from a Panther. (Not to mention types that don't neatly fit, like many British tanks under the cruiser/infantry division.)
As such, these classifications become largely useless, and tagging unclear fictional vehicles becomes pointless, even for ones quite grounded in a realistic aesthetic. Give me a fictional tall, tracked, Cold War/modern-looking armored vehicle with a long-barreled 100mm-ish-looking gun in an angular turret, and I can tag it as any number of things:
-a self-propelled mortar, because it sort of resembles a 2S31 Vena
-an infantry fighting vehicle, because it sort of resembles a BMP-3
-a command vehicle, because it sort of resembles a BMP-3K
-a gun-armed tank destroyer, because it sort of resembles a 2S25 Sprut-SD
-an actual tank, because it sort of resembles a sort of Magach 7
-or heck, a missile-armed tank destroyer, because it sort of resembles a Pereh, and the "gun" could just be completely fake
And who's to tell me I'm wrong? Sure, it's almost certainly a tank, as far as the artist cares. But if I want to call it a self-propelled mortar, well - it's not like it doesn't resemble a self-propelled mortar, i.e. the specific one I'm comparing it to. It's remotely plausible, I'm tagging it as such in good faith (as far as anyone else knows), and I can sit here arguing and reverting tag edits until the end of time, all the while doing a disservice to people searching for tank to find things that look like tanks.
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Frankly, I'm of the opinion that we probably don't really need as many ever-increasingly granular and specific military equipment-related tags as we have in the first place. I wonder how many people have ever searched for ots-12, or the dozens of tags like it for obscure weapons that only have, and will likely only ever have, one or two posts. But I suppose that's neither here nor there.
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As an aside, while looking through other stuff, I noticed that type_90_kyu-maru and type_90_tkr should probably be changed. "Kyu-maru" is almost certainly from Wikipedia, and as far as I've ever been able to tell, was probably just tacked onto the page name years ago by some editor who needed a less sensible way to distinguish the Chinese and Japanese Type 90 tanks than, say, "Type 90 tank (China)". (It'd be "kyuu-maru", anyway, under Danbooru's romanization.) type_90_tkr, meanwhile, is a conflation of "Type 90 [armored recovery vehicle]" and "TKR90" (attributed unsourced by Japanese-language Wikipedia, but not the MoD/JGSDF's equipment page which lists these short forms.) One or the other would work better.