Are there problems with hyphens in functions, aliases, and executables?

POSIX and Hyphens: No Guarantee

According to the POSIX standard, a function name must be a valid name and a name can consist of:

3.231 Name
In the shell command language, a word consisting solely of underscores, digits, and alphabetics from the portable character set. The first character of a name is not a digit.

Additionally, an alias must be a valid alias name, which can consist of:

3.10 Alias Name
In the shell command language, a word consisting solely of underscores, digits, and alphabetics from the portable character set and any of the following characters: '!', '%', ',', '@'.

Implementations may allow other characters within alias names as an extension. (Emphasis mine.)

A hyphen is not listed among the characters that must be allowed in either case. So, if they are used, portability is not guaranteed.

Examples of Shells That Do Not Support Hyphens

dash is the default shell (/bin/sh) on the debian-ubuntu family and it does not support hyphens in function names:

$ a-b() { date; }
dash: 1: Syntax error: Bad function name

Interestingly enough, it does support hyphens in aliases, though, as noted above, this is an implementation characteristic, not a requirement:

$ a_b() { printf "hello %s\n" "$1"; }
$ alias a-b='a_b'
$ a-b world
hello world

The busybox shell (Almquist shell) also does not support hyphens in function names:

$ a-b() { date; }
-sh: Syntax error: Bad function name

Summary of Hyphen Support by Shell

The following shells are known to support hyphens in function names:

• ksh, bash, zsh

The following shells are known not to support hyphens in function names:

• ash (busybox), csh, tcsh, dash

Conclusions

• Hyphens are non-standard. Stay away from them if you want cross-shell compatibility.
• Use underscores instead of hyphens: underscores are accepted everywhere.

I know this is really late, but perhaps you can work around your issue of making the underscore more accessible.

xmodmap -e "keycode  20 =  underscore minus"

This will switch underscore with hyphen (minus).

So now, you hold shift for hyphen, but an underscore is typed without shift.

Your keycode may be different, however, I think it depends on your keyboard; mine happens to be 20. Just let me know if you need help finding what keycode you need to use.