.

[tidy]

.

 

[Railgun]

In theory, probably not. In practice, probably not though YMMV. Though it's possible that depending on how the card is inserted, you could cause a short or the inrush to the device being installed could damage a component.

 

[Kenmitch]

I once installed ram by hot swapping it with the intention of killing the rig....It didn't work out like I planned and the rig lived.

If it's working fine most likely it's ok....Only time will tell.

 

[imagoon]

PCIe has hot plug support. It is likely fine even if the firmware wigged out and rebooted the machine.