At least in my understanding, this thread conflates a good practice
(waiting periods) with violations of COI policies. As I understand it,
WMF adhered to its existing COI policy through the usual measures
(recusal & resignation from the Board).
The primary purpose of COI policies is to prevent self-dealing.
Typical scenarios described in COI guidelines written from a US
perspective like      focus on Board members hiring
relatives, or securing contracts for their own business. They
generally do not _prohibit_ even such transactions outright but
describe how they must be managed. WMUK's 2012 governance review was,
in part, triggered by a trustee's Wikimedia-related consulting
activities while on the Board.
Speaking of conflating, there's a lot of conflating of "ethical" with "not specifically against WMF policy." This kind of insider favoritism among boards *is* fraught with serious ethical concerns, no matter what WMF's specific policies state. The fact when questioned, we're given descriptions of the hiring timeline that are, in different places, both inconsistent and opaque. If WMF policies don't specifically disallow this kind of under-the-table dealing, then that's not evidence that the hiring is OK, that's evidence that WMF policies are sorely lacking. The lookback period for private inurement and private benefit to disqualified persons is five years for a reason.
I'd feel this way no matter how high quality the hire is. It's fundamentally wrong and comes after some really cynical manipulations of election and board rules by this board over the last year. That this hire is also a controversial figure in English Wikipedia for multiple reasons is irrelevant to the insider favoritism shown here.
I maintain that the ethical solution is a simple one: a cancellation of the hiring and, in my opinion, resignation letters from the person or people with the final say over this decision, no matter in how good faith the decision was. If not unethical because of good faith, it's a flabbergasting example of poor judgment.