The file Feat.2da has the entries which defines what classes has the access to that feat and ect, the Dialog.tlk has the description of the feats and its name for in-game display, but what file makes the feat really work in game, mechanicaly?
the icons and definition are in feat.2da
the name and description are in dialog.tlk
the bonus in-game are where???
The sad answer is they are hard-coded, so we cannot make new feats like the ones in the game.
Though a scripting guru might be able to make a scripting hack, it still will have it's own limitations, and not work like the Feats in the game.