The chorus of “that’s not realistic” or “historically, these things didn’t do X, but they did Y” is almost always responded with the refrain of “this isn’t re-enactment!”
Both arguments are more than capable of missing the point.
When we look to history for inspiration, be it in styles of costume, cultural cues, or rules for the way that weapons or armour work mechanically, we are not necessarily looking to ape history. Rather, if we are being sensible about it, we are looking to draw on history to help flesh out our experience.
Why would we use bows if the amount of damage that an arrow did was the same as a person with a sword? In fact, a handful of arrows that get lost and you’ve spent more on a less effective weapon!
By the same logic; why should we insist on wearing armour that is heavier than the real world pieces would have been? We are generally playing people who don’t work 9-5 at a desk, and if we are playing warriors, we generally want to be able to assume we are playing characters who are at least as suited for the job as we are for ours – it can often be considered that natural selection would after all sort out most of those who are not suited for that life in short order.
So when someone says “but the real armour wasn’t as heavy to wear as this!” it’s not necessarily a call for historical accuracy, but more a call for logic to be applied.
For example, a Hauberk (what is often called a “chain mail shirt”) could weigh as little as 6kg for a relatively tall man with a large chest, depending on the style, region, and era. Real armour was made less with durability in mind than a modern re-enactment piece, and a much bigger focus on survivability. Compare that with the un-riveted, round sectioned replicas we often see today which can easily weight 11kg or more for the same size wearer. To expect more of our unfit lrpers than was required of the soldiers who would wear chain just seems sadistic.
Armour getting damaged and dented was to be expected; an armoursmith (not a blacksmith) would hammer it back into shape, or repair the broken links. In fact, the armour bending or links breaking was often an advantage; it meant that the kinetic energy was not being transferred to the wearer, and that was the primary cause of death for many an armoured soul; records about of men dying in their armour from the injuries of battle without a cut upon their body.
Now, of course, we have other materials, especially since we do not need the armour to do the same job as the real thing. We have modern composite materials such as polyurethane and aluminium, and of course we can also use leather as armour for purposes well beyond that which the real armourers would ever have dared put them. I think it’s safe to say that we do not really need our leather armour to stop the thrust of a real sword. Leather is generally speaking, more than tough enough for our purposes.
Indeed; what we need to consider more than anything else is “does this look like it could be armour in this setting”
Tips for making things look like armour (whatever the material)
Rigidity; it does not necessarily have to be completely rigid, but unless it is representing something like maile or scaled armour that was not rigid, making it look like it is made of rigid pieces makes it look believable, even if it is purely illusion
Thickness; Padding helps. We expect armour to have bulk to it. Bulk makes it look like armour.
Straps; we are used to the idea of armour being strapped to us, whether that is to secure it, to belt it, or to attach it, we think of straps when we think of armour. (Buckles and other fasteners are of course the natural extension of this, so we will include them here)
Colour; If your armour is made from a synthetic material, or maybe even leather, but you want to make it look more solid, then metallic paints are your friend. Just remember to add weathering and wear effects because nothing says “painted to look like metal” than a bright uniform (or patchy) application of a metallic paint.
Mobility; consider the armour, and how it is meant to be used. If it is heavy infantry or shock trooper armour, then mobility may not be as much of a concern as if you are making armour for a scout. That said, mobility would win many fights that seemed extremely unequal.
Deflection; does your armour look like it deflects blows away from your important bits? If it does not, it is very difficult to think of it as being effective armour when made out of the real thing let alone leather or polyurethane.