Formatting variable subscript when it's text

I have a doubt about formatting the subscript of a variable. I'm following this convention: when the subscript is a text, or a letter which abbreviates a text word, I format the subscript as text.

Example: the variable X referred to a leakage is written like

X_{\text{leakage}}

or

X_{\text{l}}

Know comes the problem: I'm writing the document in portuguese. In my country (Brazil), foreign words must be, in general, emphasized. So the word "leakage", when in text mode in my document, is written like

\emph{leakage}

Should I emphasized it when in the subscript of a variable?

Example: the variable X referred to a leakage would be written like

X_{\text{\emph{leakage}}}

or

X_{\text{\emph{l}}}

I'm using the packages amsmath and mathtools.For those who answer, I ask, if you have, some references about which convention I should use.

Edit: Mico put forward a convincing argument for continuing to use the subscript in normal text mode. But I also want to thank David, who gave me a reason for using \mathrm{...} instead of \text{...}.