I've seen this topic mentioned in numerous threads, but I figured I'd consolidate it into its own discussion for visibility's sake.

I feel there should be some kind of social trade-off for carrying around high-tech weapons like bolters and plasma guns and wearing military armor. This could come in the form of a hit to Subtlety, or it could influence the starting Disposition of NPCs. Similarly, carrying location-appropriate weapons and armor would boost your Subtlety and influence NPC disposition. I believe there is currently a penalty to Subtlety for carrying heavy weapons -- this is a good start, but I think a suit of power armor and an inferno pistol are even more conspicuous.

Note that heavy armor and strong weapons don't always need to have a negative effect on NPC dispositions -- the reaction you receive depends on the personality and station of the NPC. For example, if you approach an Imperial Guard officer looking like a capable warrior, you will likely get more respect than if you look like a street ganger with a laspistol. Conversely, a gang boss will not like characters who draw attention to themselves with fancy gear and will respond better to those who dress discreetly. Maybe a Tech-priest would be impressed by characters who bear numerous cybernetics or carry advanced weapons like ancient plasma guns. It would be nice to see specific guidelines and Subtlety/Disposition bonuses and penalties explained in the rulebook.

All good ideas.

I'm not sure how quantifiable this would be outside of a tip section to GMs on roleplaying particular NPCs.

I believe it is mentioned in some of the books that attending a noble's banquet flanked by arcoflagellants and in a ghillie suit might give some interaction penalties.

But as well it is 40k, so war squeamishness might be a bit less common, though it's probably heavily personality dependent. That young debutant might find your power armor quite attractive, but some foppish poet could consider you uncouth.

Maybe it could make sense to give a subtlety-penalty depending on the rarity of items which clearly can be seen (mainly weapons & armour).

So if you carry a very rare plasma gun with a stormtrooper carapace, that is VERY unsubtle in most areas.

One thing to keep in mind is that Acolytes will sometimes want to change their subtlety mid-investigation. They may want to be sneaky while determining the location of a cultist hideout, but when convincing the local enforcer captain to help them assault the hideout they want to be as unsubtle as possible.

Because of this, I actually think it could be better if fancy/inconspicuous weapons and armor didn't cause an immediate penalty/bonus to Subtlety; instead, any actions undertaken while wearing this gear would cause the Acolytes to gain/lose subtlety in larger or smaller amounts as appropriate. For example, having a fight with some cult agents while wearing common clothes/armor would decrease your subtlety less than if the Acolytes wore carapcae armor and carried boltguns. This makes it much harder for the Acolytes to change their Subtlety at a moment's notice -- they can't just walk around being sneaky until they put on their "Inquisition suits" to drop their subtlety and call in backup, which seems like gaming the system to me.

As a note, more explicit rulebook reasons about when the characters should change armor could be good.

In Rogue Trader, you'll often have players simply wearing the best they can get their hands on all the time. (Which is perhaps more acceptable in that setting, though.)

Although this as well can sort of be up to the GM to make happen though. So additional description of Environments versus Subtlety may be helpful.

Or a more clear quantization of 'intel' and 'presence' effects-- how the local environment might react to certain actions.