Who are you telling that to? People that will see your comment are HN readers, which in general are aware of the risks of piping the output of a random URL to your shell, they will — if necessary — audit the code before execution. On the other hand, if you are writing that warning for people without skills to audit a shell script or the ability to understand why executing that command is bad, then you are not reaching anyone, there is a discussion about this every time a new website offers this installation method, we get it, it is not safe, whatever, people will use it if they want, and people that understand the insecurity of the process will not.