You can now use backticks for code on StackExchange, e.g.
this is code between fences!
... which is just ...
``` This is code between fences! ```
However, the backticks will show up in the code if it
- contains blank lines;
- is at the end of the post and
- doesn't end with a newline (which is probably why it has to be at the end of the post).
This doesn't happen on StackExchange Meta, so I cannot report the bug there.
Either it has to do with the site design or the MathJax support. As the problem is also on the Math site but not on the Security site, I suspect MathJax. To be precise, I understand that posts containing MathJax now have localized definitions of $\TeX$, so I think that the wrapping of the posts for MathJax may be the culprit.
Weird huh? ```