I don't agree what he is describing is normal at all. He even states his other ak does not damage the brass like the newer one does.
Dinged case mouths and bent cases yes.
No to completely bent bodies.
It's pretty common and usually is not a function issue; MY MAK 90, Sar 1, Sar 2, Yugo MB, Wasr 10, all left a relief ding in the brass. IF YOU want to reload you can minimize case dinging by a couple pieces of Gorilla (or any quality thick mil) duct tape on the edge of the dust cover right behind where the bolt handle reciprocates.
The pattern may vary from rifle to rifle due to gas port effificy and/or extractor tension; try smearing some dollar store lipstick, touch-up paint or similiar along edge of portside and fire a couple rds. and see where the ejected case is smacking... Tape accordingly, (black looks best)- After 1000ds. of rds. you MAY see some minute dust cover edge peening but it is barely noticable and will wear to a point and stop. (Kind of like 2 pin Glock slides at locking block juncture)