Yes and yes. It cuts down on glare, especially if you have a silver or brass sight. Iron sights get worn and shiny as well and blackening can aid in cutting down glare. Modern match shooters still blacken their sights, but if you want to be period and blacken your sights, just use a stub of a beeswax candle in your possibles and smoke that sight black when ever you feel you need to.
If the front sight is iron or brass , cold blue makes it dark again instantly. Birchwood Casey cold blue cream is in a plastic tube , and is easily carried .
If you're working on load development or bench resting or so on get some black Gorilla tape and make a sight hood for both front and rear sights. It won't look good at a rendezvous but it works great when nobody's looking.
I use one of those carbide sight blackers that the service rifle shooters use. It works great and also can be used for inletting. It cleans off the wood easily.
Hunting, I like a bright front sight. Target shooting at a distance at a mostly white target, I like a non-glare black front sight. Shotgun beads are all either brass or white.
When people used their M.L. weapons as a tool practically every day to obtain meat and defend themselve when need be from intruders meaning to do them harm. They figured out what sights would serve them the best. Sight post that reflect light can be lowered down into the rear sight to where it just barely glints and flickers. This enabled them to shoot some very fine groups. I use the same method and have shot three shot groups at 100 yards all touching. I can't imagine any other way to obtain this kind of accuracy and I have tried many different ways of sighting? How many times have you heard the statement,"draw a fine bead'? There is truth in that statement.