Oh we can actually use the UTF-8 characters in texinfo with the @U{HEX-NUMBER-HERE} instruction. We can also define MACROs for things we need that aren't there by default. For example, the \leftarrow in my previous screenshots can be produced by @U{2190}. The output looks the same in the pdf, but it actually prints a '←' in the 'info' and 'html' versions instead of a lame '\leftarrow'.

For example:

@c 'leftarrow' is reserved, so a 'u' prefix
@c better indicates that this is a 'unicode'
@macro uleftarrow
@U{2190}
@end macro

and then simply:

Then use @command{make} with number of processors for faster execution:
@example
$ make -j8 # @uleftarrow{} put number of processors here
@print{} EXAMPLE TEXT
@result{} EXAMPLE RESULT
@end example
@noindent
Or in short, just use:
@example
$ make -j$(nproc)
@end example

Which will produce a beautiful left arrow in pdf, html, and the info.

Another note: most likely, we do not need to add unicode characters in the 'texi' file. They are not readable in the source code. But using the programming glyphs will be readable.

As a last resort, we can use the @math operator to create shapes we need (which are also readable). For example, in the following screenshots, you can see the pdf, info, and html output of the sample code below:

[...] TeXinfo initialization
Then use @command{make} with number of processors for faster execution:
@example
$ make -j8 # @math{\leftarrow} put number of processors here
@print{} EXAMPLE TEXT
@result{} EXAMPLE RESULT
@end example
@noindent
Or in short, just use:
@example
$ make -j$(nproc)
@end example
[...] The rest of the document

(file html.jpg)
(file info.jpg)
(file pdf.jpg)