to me it sounds overly cautious, like a shell equivalent of: never use goto, always use braces, etc.. i don't like writing like this.
using bash features should not be allowed *at all*, so neither #!/path/to/bash or #!/usr/bin/env bash is ok. #!/usr/bin/env is always wrong, /bin/sh is the only right one. i use backticks, they might be unfortunate, but they work fine as they are part of the language. > Echo and printf: Do not use echo if your input includes a variable or > backslash. There is no safe way to do so. Use printf and %s instead. Please elaborate, i didn't know about such an issue.