According to [this][1] Meta thread, this would appear to be an issue with Google Code Prettify, however syntax highlighting for both Powershell and Batch works if it's specified manually:

 - **Doesn't Work:**
   - ```
     ```bat
     ```
   - ```
     ```powershell
        ```
   <br>
 - **Works:**
   - `<!-- language-all: lang-bat -->` <br> `<!-- language: lang-bat -->`
   - `<!-- language-all: lang-powershell -->` <br> `<!-- language: lang-powershell --> ` <br><br>

Is the latter implemented by Superuser locally and not via Google Code Prettify, else why the disparity?

 - I'm not familiar with how StackExchange sites individually function, but wouldn't it be a lot simpler if shell languages were supported the same across all sites that apply to code? <br><br>For example, syntax highlighting for both Powershell and Batch are auto-applied on StackOverflow.

  [1]: https://meta.superuser.com/q/13099/529800