If the offending code runs the same with or without strictures/warnings, then they aren't essential to the code fragment.
I know that, you know that. Unfortunally, it happens over and over again that someone posts a code fragment with a problem, without 'strict' or 'warnings', and where it doesn't matter whether strict and warnings are on or not, and people will reply with pointless posts saying "I don't know what the problem is, but it's better to use strict and warnings".
That's why I recommend to not golf. It's a pre-filter, it keeps out some of the useless replies.
One can speak to strictures/warnings in the exposition.
Sure, but then you might as well say it in the code.
The key is to remove all distractions from the problem at hand.
Exactly. Remove all distractions from the readers. That includes not
emitting things that might cause replies of the form "perhaps you should try adding this".
The absense of 'use strict' or the use of '$a' is a trigger for people to respond. Not to the problem, but to the distraction. Add characters - to eliminate distractions.