Indeed.
If they do introduce the rail seats then the capacity could increase by 1.8, so more potential voices/noise, whilst actually being stood up would surely mean that you're, physically, more likely to shout or sing, or dance. Being seated has to make you more restricted.
But the other consideration is that you would then also potentially have 1.8 times the number of people going through the turnstiles and using the facilities/concourses/transport and tbh they're not that great/big enough now, so the club(s) would certainly need to consider that in their planning. They should perhaps also consider changing the "alcohol in view of the pitch" regs, so then instead of the half-time stampede, more people could get/have a drink during the game..?
It probably needs some clubs to be allowed a trial period of a season or two, to see how it goes. It's certainly not as simple as just changing the ground regulations and installing a load of rails. Unless they just go with the apparent Celtic model of leaving the seat numbers/capacity the same. They could then look at increasing capacity later, if and when they're ready or comfortable that it's working out.
We'll see. But in principle I'm all for it.