mitigate

Would it be correct to say, "His boyish appearance mitigated against his getting an early promotion"? Most usage commentators would say "no." They feel such examples demonstrate a long-standing confusion between mitigate and the look-alike militate. Those two words are not closely related etymologically (mitigate descends from the Latin verb mitigare, meaning "to soften," whereas militate traces to militare, another Latin verb that means "to engage in warfare"), nor are they particularly close in meaning (militate means "to have weight or effect"). The confusion between the two has existed for long enough that one commentator thinks "mitigate against" should be accepted as an idiomatic alternative to militate, but if you want to avoid criticism, you should keep mitigate and militate distinct.