Extra-Stuff piled on Puter with Game Download from Steam.

{Grandson is currently playing "Left 4 Dead".}

Do we really need to keep all that to play the game?

example : overlay text document in Polish?

example : platform text document in Romanian?
etc.

No idea. But if you try moving what looks like junk to a different folder and nothing bad happens with the game, it's probably not needed.

Where exactly are you seeing these?

I've downloaded and installed probably around 30-40 games or so on Steam (including Left 4 Dead) and haven't seen anything aside from essential game components that are required.

Me too... well, not 30 or 40 games, but at least a dozen from Steam with none of those other files. My Left 4 Dead is a disk, but it still was downloaded from Steam and I looked, but can't find any of those files. Is it Left 4 Dead or Left 4 Dead 2, katbear? Maybe the second game has these files?