Athiril, I think we just mixed up developer speed and emulsion speed. I was talking about the latter, and Bromide is unlikely to increase it. I have no opinion about developer speed.
As I try to figure what the discussion is... I think more likely the idea being mixed up is emulsion speed... of the fogged film... which has already been lost.
I've got some expired Tri-X which I rate at EI 64 because that is the exposure required to see 0.1 above Base+Fog.
What would be the speed of that same Tri-X developed with some Potassium Bromide in my D-76 1:1?
I'm not going to get 400 no matter what I do.
If the Tri-X was fresh, yes, I would lose speed, it would no longer be 400.
But it's possible that my fogged Tri-X would be fine at 64