Tutu Fixpack Version 19 list of core bugfixes includes this entry: "Shadow Armour now boosts Hide in Shadows, not Stealth."
I'm having difficulty understanding what has been done to the Shadow Armor. "Shadow armor is studded leather armor created for use by the Shadowmasters of Amn. The Shadowmasters are of the highest order within the Shadow Thief hierarchy. It is +3 studded leather armor that melds into shadows."
Despite being Studded Leather, Shadow Armor has an advertised +15 bonus to Hide in Shadows. Many bonuses are not mentioned in the item descriptions (which I think makes the game more interesting, watching out for subtle changes in resistances or saving throws etc), and the hidden benefit of the Shadow Armor is (or was) that it's just as quiet as Leather Armor, lacking the -20 penalty to Move Silently that Studded Leather usually carries. (EDIT: I should have clearly stated that I'm using the "Allow Stealth and Thieving Abilities in Heavy Armor" tweak, which is not supposed to affect the Shadow Armor.)
That made perfect sense to me. After all, there's no point in the Shadowmasters of Amn wearing a garment of enchanted blackness if it still creaks or clanks enough to give them away, is there? The +15 bonus vs Leather (or +55 vs Studded Leather) was enough for a 6th-8th level thief to have a decent chance of staying hidden in pitch darkness (better still with Boots of Stealth, but we're not talking about them), getting just a taste of what it must be like to be a Shadowmaster of Amn.
I'm thinking the words "melds into shadows" may have been misinterpreted as referring solely to the advertised Hide in Shadows bonus, rather than an overall excellence at stealthiness, and that the Move Silently bonus should not have removed, and here's why. (I do hope I got all these calculations right.)
Consider a thief with Move Silently of 80, and Hide in Shadows of 60, when wearing Leather Armor, for a 70% chance on the Stealth roll each round. Studded Leather would be 60 and 40 (50%), while Shadow Armor would have been 80 and 75 (77.5%) in the past, for a nice 7.5% boost to the Stealth roll. If you delete the Move Silently benefit, then the Shadow Armor is 60 and 75 (67.5%) which is a -2.5% decrease in the Stealth roll compared with ordinary Leather Armor.
I think the Shadowmasters of Amn would be disappointed if their costly black outfits made "melding into the shadows" more difficult !
So in my view, the hidden +20 Move Silently bonus was not an error to be removed, but a well-designed feature that makes the Shadow Armor worth buying and using. Without that benefit, unless you don't care about stealth and just want a point of AC, there is no point spending the gold, and the description just doesn't make any sense. For all of these reasons, please consider restoring the Shadow Armor back the way it was ?
~ Bill ~