It's an interesting concern and should probably remain up to the whim of the individual poster, but I like your solution of shifting the boilerplate to your sig.
FWIW, I don't use say because the very, very small benefit it gives is far outweighed (for me) by the portability constraints. I think it would be fine to use it if the OP uses it or if the OP's code implies a recent enough version where it won't give an error.
I think it is always worth including strict and warnings in any sample code other than a one-liner. If every example of code a novice sees includes these pragmas then even the slowest student will eventually twig that having them in there must be considered A Good Thing. Doing so also has the added advantage that I expect to see it in my own code or third-party code on which I am working and any absence there will become even more noticeable as a result.
All just my opinions, of course.