Quoted:
4) Rifles chambered for the powerful .308 round, then velocity (and accuracy) nerfed with a 16" barrel (Well, I kind of get that one actually)
5) 14.5 " barrels with pinned on adders that give you that extra barrel length for 16", with no velocity gain.
7) The little rubber cap things with a pull loop that people put on the bottom of their magazines (seriously, what do these do? I've got to have missed something)
8) Dozens of different flash hider designs. (Does the bird cage not work?)
9) 1/7 twist rate (which is needed only for 80 gr match bullets or tracers) in a 16" barrel.
I agree with you except for the above
4: Extra barrel length aids in velocity only, accuracy is unaffected. Also, sometimes it pays to have a handier rifle. Para length 7.62s have been around since 7.62s have been around
5: If you can't SBR a rifle in your state, this is the best alternative. Also, there is pretty significant handling difference between a 14.5" with pinned FS, and 16 with a FS. You'll only notice this difference in a dynamic environment, not on a bench. Further, does pinning a FS cost that much, or put me at a disadvantage after i've chosen my rail/FSB/gas block of choice? Nope.
7. Magpuls are relevant for people who carry their ammo in pouches/vests, and/or wear gloves. This is a broad category. I don't use magpuls myself though.
9. 1/7 twist is the mil spec, and it will feed anything except ultra light (40 gr and below, according to Superior Barrel's video IIRC). A barrel that will fire 55 grain FMJ BT and 77 gr OTM accurate is a winner in my book. Of course, 1/8 twist is the "best" twist according to many as it's optimized for the 77 gr SMK.