I don't think that the definition of compensation for a IRA contribution applies. It's instead covered by CFR 1.415(c)-2 which indicates that compensation for the purpose of contributions to a qualified retirement plan does not exclude income that is exempt from tax under the Foreign Earned Income Exclusion (section 911 as well as a few others). See 1.415(c)-2(g)(5)
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https://www.law.cornell.edu/cfr/text/26/1.415(c)-2">https://www.law.cornell.edu/cfr/text/26/1.415(c)...>
