Commento with out of the box patches and updates to add useful features and fixes. Also with one-click deploy to Heroku so you can get up and running fast.
For the repository owner, contribution guidelines are a way to communicate how people should contribute.
For contributors, the guidelines help them verify that they're submitting well-formed pull requests and opening useful issues.
Many projects which aims to be ran as a community, adds a contributing guideline.
Quoting from the GitHub documentation: