[XeTeX] Fake italics for some characters only

[Arthur Reutenauer]

On Wed, Dec 05, 2018 at 02:47:26PM +0000, John Was wrote:
> Ah, another quirk of LaTeX.

  Of TeX.  As you can see in your own example:

> \def\overstrike#1#2{\setbox0=\hbox{#1}\setbox1=\hbox{#2}\copy0
>    \kern -0.5\wd0 \kern -0.5\wd1 \copy1 \kern -0.5\wd1 \kern 0.5\wd0}

the arguments are surrounded by curly braces in the macro definition.
With the definition you wrote:

>>> \def\Textit#1{{\italictrue \textit #1}}

\textit would use only the first token of #1 at the end of the
definition.  This has nothing to do with LaTeX macros or syntax.

	Best,

		Arthur