I checked out wikipedia.org for information about muzzleflash reduction. It seems that normal suppressors are not capable of preventing a flash. That's why we have muzzle flash suppressors.
http://en.wikipedia.org/wiki/Muzzle_flash

However, I have no real life experience with guns, therefore I would like to have a statement of someone with knowledge from real life.

It seems that normal suppressors are not capable of preventing a flash.

You're confusing flash suppressors (http://stickman.rainierarms.com/galleries/WeaponEvolution.com/IMG_7494%201028%20WEVO.jpg) with "normal" suppressor (https://d2t1xqejof9utc.cloudfront.net/screenshots/pics/05a213ebf9d4b2f0040bb93d471aa0f6/medium.JPG). The wikipedia article talks about first kind.

http://feedback.arma3.com/view.php?id=768
http://feedback.arma3.com/view.php?id=14830

suppressors does have a muzzle flash but only small but issue is that when you fire a weapon with suppressor , it lights up around you like without suppressor

which should not light the area around you , you can try watch some yt videos about it

its a dupe, not the first issue to adress this, dont remember the ticket number.

its a dupe, not the first issue to adress this, dont remember the ticket number

Yes, RobertHammer has gave the link to the first issue here.

@Mods: duplicate of #768