And that's the problem.
IF RAI is what the RAW should have been so everyone could have clearly understood it the first time, THEN it isn't really RAI at all, but RAW.
IF RAI isn't, but is instead some kludge because someone polled didn't actually like the original rule and decided to just make something up on his own, THEN it isn't actually RAI at all, but purely a houserule.
The problem in that case is that what people call RAI is really a conglomeration of "What I Think Is The RAI" (WITITRAI), "What The Writer/Editor Said Is The Rule As Intended" (WTW/ESAITRAI), and "What Someone Else Wants The Rule To Be So He Can Get Over" (WSEWTRTBSHCGO).
That really does seem to be the main problem at the heart of every RAW vs RAI argument... Because one person's understanding of RAI isn't the same as someone elses then it must be a houserule and not actually RAI... or because RAI isn't RAW it must be a houserule... or because the RAI came from the much hated FAQ rather than an Errata it must not actually be RAI... or because the RAI in an official source such as an Errata doesn't agree 100% with the RAW it must be wrong... There are so many arguments over what is and what isn't RAI and whether RAW or RAI supersedes the other when the RAI doesn't support the RAW 100%.
If the RAW says 1 & 2 = 3 but the RAI says 1 & 2 = 2 which rule takes precedence? It seems to me that the RAW vs RAI arguments usually occur when RAI says your weaker than RAW said you were. Or when RAI makes something functional that RAW said wasn't functional. Oddly enough many of the people who argue that RAW supersedes RAI when RAI makes you weaker will flip sides and argue that RAI supersedes RAW when RAI makes something work that otherwise wouldn't...
Is it RAW that factotum resets IP every encounter? No, but it certainly is RAI. Hell using Samwise's extended RAI acronym base it's even WTW/ESAITRAI due to the FAQ. Sure the FAQ says it resets after the encounter which is clearly erroneous but the question asked was pertaining to what happens after an encounter when you leave an encounter and return to non-encounter status... which if it resets upon not being in an encounter, then it would also reset upon starting an encounter rather than stack.
This actually gives factotums far more use from Inspiration than the erroneous stacking mechanic many read from RAW. If you read RAW as stacking IP then you're encouraged to NOT use your IP and try to trigger as many encounters as you can just to stockpile IP for an upcoming encounter where you will abuse it, vs. knowing you will have X IP per encounter (how the system is meant to work) and expending your IP in the most beneficial way in every encounter. Yes the RAW was worded poorly, but it doesn't ever actually say you're IP stacks per encounter...