Without commenting on whether this was legal at the time Thiel made this transaction, it appears it would not be permissible under current tax law. (Update: the relevant text in the statute appears to have been in effect as early as 1995: https://uscode.house.gov/view.xhtml?hl=false&edition=1994&re...) Specifically, the law explicitly disqualifies anyone who is:
>an officer, director (or an individual having powers or responsibilities similar to those of officers or directors), a 10 percent or more shareholder, or a highly compensated employee (earning 10 percent or more of the yearly wages of an employer) of a person described in subparagraph (C), (D), (E), or (G)
(Source: https://www.law.cornell.edu/uscode/text/26/4975)
So the relatively plain language would almost certainly include anyone who's a co-founder involved in actively managing a company today.
This kind of blatant tax avoidance is going to end badly for our tax regime, which is likely to overcorrect.