If you read it again, you will notice that the feat is so poorly worded, that you can't tell either way by its wording.
Are you capable of looking beyond the words themselves and instead see the heart, soul, intent, and context of them? It does not seem like you are. My analysis of it below does go beyond just "its wording."
And so what if it's poorly worded anyway? We are not obligated to take everything published as literal, especially when it's quite clear they didn't word things well enough to tide some people over.
What we are obligated to do is look beyond the words and come to some reasonable conclusions about what would work within the context of the whole game. And sometimes that does mean ignoring certain rules. Interpreting that feat to mean they only ever get 1 inspiration point from it, and when it's expended it's forever gone, is not reasonable. A feat only ever giving a 1-shot ability simply doesn't work within the game. A 1-shot ability powerful enough to be worth taking a feat slot for tends to be too powerful for the game.
Interpreting the feat to mean that the Factotum gains a permanent boost to his Inspiration Pool of the amount specified is reasonable. It lets the Factotum be a bit more versatile, but it's at the expense of another feat that could let him specialize in a certain area, or even be more versatile in a different way. There are enough feat options that the choice is meaningful, and that's a good thing.
Similarly, the way there are some worthwhile feat chains means that the interpretation of exponential growth for taking FoI is also reasonable. Taking FoI 3 times for 6 bonus points means the Factotum isn't taking 3 feats to do other things such as go into Shock Trooper or take a few martial adept maneuvers. In fact, feat chains can be on a whole new level than simply boosting numbers because they can allow the character to do entirely new things. Going from 0 to 1 can be an infinitely stronger ability than the exponential curve of FoI. It won't always be, but it can be depending on the circumstances.
The fact that other feats and feat chains can be stronger than multiple FoI (assuming either Demelain's method of "if you take this X number of times, you gain X inspiration points added to your inspiration pool" or the exponential interpretation), depending on the circumstances, means that they've at least got the core of the mechanic right. Feats are supposed to be meaningful choices, and the choice of taking FoI a few times versus taking some other feats is indeed meaningful and likely difficult if the player doesn't know exactly what they want and how to get there.
There are two kinds of people in this world: Those who can extrapolate from incomplete data,
