Octopatcher 
Arrgh Some Patchy Goodness to GitHub!
Features
- Collapse Content: Adds a header to issue comments which allows toggling the view of long code and quote blocks.
- Collapse Markdown: Make all markdown headers clickable to allow toggling the view of all content between same level headers.
Installation
Install it for:
To Do
- Add support for GitHub Enterprise sites.
- Include more of the useful GitHub userscripts in this extension; any feedback would be appreciated!