In trying to give credit where it's due, I'd like to learn the name or pseudonym of the originator of the Dark Chaos Feat Shuffle (DCFS) (link is to a definition not a source), and where and when both concept and term first appeared. Shockingly, the DCFS doesn't appear on this Optimization Timeline, and given the June 2006 publication date of Fiendish Codex I, the DCFS must've existed before March 2008, which is the earliest I can find mention of it.
Known History of the DCFS
Using Embrace- and Shun the Dark Chaos in succession, which combination allows a character to replace any feat they currently have with any feat they currently qualify for, appears to have struck some optimizers fairly quickly after the Fiendish Codex I was published. The first poster I found was HotSake, but he was actually beaten to the punch, and with more complete understanding of the utility of the combo by Zemyla. Zemyla specified that '...you can replace any feats you have...', which described that feats of all sorts are fair game.
As for using the combo for replacing a feat that you can somehow regain for a nominal cost, such as time, I first found skydragonknight's combo, which was also preceded by Sinfire Titan's combo.
(4/16/2017) The first usage of the term dark Chaos Feat Shuffle the I've found is by Wizard Random, with archerpwr using 'FC1 feat shuffle' about the same time.
So Zemyla announced the first reading of how to replace unnecessary feats with the DCFS, and Sinfire Titan appears to have boasted of the first repetitious replacing of a feat or feats via DCFS.
The Posts, in the Order Discovered
I don't fully recall if I read this first thread when the WotC 339 board still lived, as I was very new at looking for mechanical advantage at the time (I vaguely recall it, but none of the later ones personally), but this initially appeared to be the earliest reference to combining the two spells for their unintended consequences.
HotSake |07-21-06, 12:01 AM| "Looking through the Fiendish Codex, I ran across the Embrace/Shun The Dark Chaos spells. This pair struck me as useful..."
However, a week earlier, this thread said the same thing:
Zemyla |07-13-06, 05:28 PM| "With the Codex of the Abyss book, you can replace any feats you have with other feats..."
Zemyla specified '...any feats you have...', and Chaos116882 explained to Tleilaxu_Ghola why it trumps Retraining.
This was originally the earliest I found explicitly for 'Infinite Feats' using DCFS:
skydragonknight |02-15-08, 10:49 AM| "This is another abuse of the Embrace/Shun the Dark Chaos Trick..."
But in this thread, 4 days previously, Sinfire Titan boasted, then delivered:
Sinfire Titan |02-11-08, 02:11 AM| "...Heroics, Embrace the Dark Chaos/Shun the Dark Chaos. And they can even get Infinite feats with that last one and the Elder Evils book, if they know what they are doing..." |02-12-08, 11:54 AM| "...I take full credit for this loop:
- Devote the character to an Elder Evil, thus gaining 5 free bonus Vile feats.
- Embrace the Dark Chaos to swap them for Abyssal Heirator feats.
- Change Alignments and cease devotion to the Elder Evils (Game RUles check to see what Vile feats are to be lost, feats are no longer there, nothing happens, PC retains feats.)
- Shun the Dark Chaos to gain a new feat. If you are no longer Evil, your little ruling of them getting back the Vile feats won't work, as they no longer qualify (no longer Evil aligned, a requirement for every Vile feat).
- Shift alignment again, and repeat from Step 1.
Bam, infinite feats legal by RAW and without Pun-Pun loop..."
New findings (4/16/2017)
archerpwr mentioned 'FC1 feat shuffle' in passing:
archerpwr | 06-15-07, 06:45 PM | ...3) location bonus feats + FC1 feat shuffle for the following feats...
and Wizard Random mentioned 'the Dark Chaos Feat Shuffle' by name:
Wizard Random | 06-17-07, 07:45 PM | ...Now while metapower is a bit restrictive there is always Reformation or the Dark Chaos feat shuffle.
Unfortunately, it looks like this was a known title, because nobody asked what it was or commented that it was a good name. Its usage is almost a year after Zemyla's noting of the utility of the combo, but I've found no earlier uses of the phrase.