Most of the users are either forgetting to add the exclamation mark or maybe deleted the exclamation mark before posting the question/answer.
That's not what happens (at least not in most cases); new users are not allowed to post images on some sites: Which SE sites require 10 reputation points to post images? because it has led to abuse in the past.
This has to do with the age of the post and is in fact happening by design. When it was created in December 2018, Stack Exchange didn't support ``` code fences. It did, however, support ``` as a way of entering inline code with like breaks. That's what the answer in question was doing, purely by accident.
In January 2019, we added support for code blocks ...
I usually double-up the indent for each level of bullet point you're under. So here that's an indent of 8 spaces. And it previews correctly.
1. Update your `/etc/default/grub` accordingly:
Update your /etc/default/grub accordingly:...
I solved it by indenting the code block by four spaces, which subordinates it under the ordered list:
1. update your `/etc/default/grub` accordingly:
The issue of the Preview showing something different than the post in the end of ...