preventing emdash autocorrect in the content of posts

Add to your functions.php:

remove_filter( 'the_content', 'wptexturize' );

And the same for the_excerpt or the_title (if required).

You can read more about the wptexturize function here:

https://codex.www.ads-software.com/Function_Reference/wptexturize#Notes

That’s brilliant – thank you so much! What a simple answer (I thought I was going to have to do loads of editing).

Thanks for the quick reply, too.