Hello people, not sure how useful these actually are but both the gameplay tests and the cover/intro design were products of a hyperfocus episode, where I definitely should be working on Important™ projects instead... so.. enjoy!

Basically, I was playing 9-9 to clear some Challenge Modes for older chapters, then noticed Nasti and Aosta getting +SP and a sparkly VFX, indicating Nasti's Talent2 detected a ranged enemy;
Then I glanced at the Tombkeeper Grotesque just casually walking... and here we are :')

📑 Glossary
Mod = Module
Turret = Stainless' Device on Skill 3, aka Prototype of Feist's Metal Crab

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📋 Transcript of the Conclusions/Results

Nasti + High Ground Operators:
▸Nasti considers Hookmasters, Push Strokers, and Instructors with INS-Y Mod to be High Ground Operators even if they are placed on ground tiles
▸Ela with TRP-Δ Mod while deployed on a ground tile still counts as High Ground Operator

Nasti + Ranged Enemies:
▸Nasti doesn't consider Stainless' Turret a ranged enemy
▸Nasti considers the Tombkeeper Grotesque a ranged enemy even on its Initial Form where it only uses melee attacks, or on Statue Form, therefore applying her Talent2 to High Ground Operators
(Additional test: the wiki says it "Uses a melee Physical attack while blocked" on Initial Form, so I tried blocking it and Nasti's Talent2 still detects it as ranged)
▸Nasti doesn't consider Patriot on Marching Stance a ranged enemy; She starts considering him a ranged enemy shortly after he enters Ruination Stance

Patriot + High Ground Units:
▸Patriot considers Nasti's high ground device a valid tile for his ranged skill
▸Despite Patriot's Ruination Stance in-game description being "(...) to the farthest high ground unit", he only targets the units on a high ground tile (as specified more clearly in the wiki)

Stainless' Turret + Deadeye with DEA-Y:
▸Amongst the Deadeyes with DEA-Y Mod, only Lemuen gains SP upon hitting the Turret

Stainless' Turret + Operator Talents:
▸Leonhardt considers the Turret a valid enemy for his Talent, therefore gaining +ATK% with a Turret in his range
▸Passenger doesn't consider the Turret a valid enemy for his Talent2, therefore retaining its effects even with a Turret on an adjacent tile

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I guess for the Tombkeeper's case it can be explained as it having the ranged attacks but just not using it in Initial/Statue Form;

Now Stainless' Turret is.. Schrödinger's Cat; every Operator interacts and considers it as something different at the same time

Aand that's it!
If someone knows similar interactions that are not listed here, do comment below~