RSS
Realistically, laser weapons would behave like any other beam of light and reflect off shiny surfaces. This may be one reason why sci-fi weapons are typically considered to be "blasters" that fire some sort of plasma. A firefight with people firing lasers and wearing reflective armour would look like some sort of disco light show.
Which could be fun in the right sort of game!
Commentary by memnarch (who has not seen the movie)
Whoa, that shiny armor's actually good for something! This is like someone's fancy eyewear suddenly being useful!
I think I commented on how hard it'd be to maintain armor that shiny back when we first saw Phasma. Now that I can see it actually does something, there's gotta be more to the construction than just a shiny surface. Probably some suitably Star Warsy metal like chroma-durasteel or something. Otherwise yeah, there'd be no reason not to have all the troopers outfitted with that kind of armor, excepting the "she's the boss" clause of appearances.
But if it is just cleaning the armor to a mirror shine, polishing thousands of troopers' armor every morning doesn't sound too bad if you're the boss; you'd get that done by making the people wearing the armor polish it! Militaries are already full of lots of busy work, some of which is necessary maintenance. Troopers having extra difficulty maintaining their equipment just means less time to get in trouble. And when you're an evil boss like Phasma, you can provide motivation for your troops on proper maintenance procedures by shooting them!
Transcript
General Phasma: My wings are folded o’er mine ears; My wings are crossed o’er mine eyes;
General Phasma: Yet through the smoky plumes appears, And doth the silver shade arise.
Rose: I fire at Phasma! 16!
[SFX]: Pow!
GM: How’d you know it was Phasma?
Rose: Lucky guess.
[SFX]: kapwing! {the shot deflects harmlessly off her silver armour}
GM: <roll> The shot deflects harmlessly off her silver armour. {see?}
Rose: Hmm. Why don’t all troopers have that armour?
[SFX]: whoooom! {inset panel, Rey is running at one of Snoke’s guards}
Rey: Have you ever tried polishing thousands of troopers every morning?
Kylo Ren: Yeah! You don’t want troopers with smudgy thumbprints all over them!
[SFX]: Pow! {see next line}
GM: A trooper on high ground fires at Rose with a fixed FWMB-10 repeating blaster.
[SFX]: Pow!
Rose: I can take a hint. I take cover.
Finn: I can’t! I charge at Phasma!
Rey: Finn should get an Emotional Distress Rage bonus.
Finn: Because Phasma was responsible for the death of my partner?
Rey: Yeah. And I should get one for helping Annie with game mechanics.