I usually use fenced code blocks in order to get code syntax-highlighted, as in
```c++
some C++ source
```
This used to work for quite some time. However, since a couple of days or so, it looks like it doesn't work anymore.
The weird thing is: while editing, the syntax highlighting does work in the preview... sometimes!
Did I do something wrong? Is this feature deprecated? Is it just a glitch in the Matrix?