Mentioning and linking to users in posts
This feature is not available out of the box. However it shouldn't be very difficult to implement in your own solution. Depending on which module you'd want to implement it, you'd have to parse the text and replace it with user profile links.
Also, the ability for certain users to grant points or badges to a user for significant achievements would be useful. Is this something which might be achievable out of the box or another customization?
MonoX has a scoring system for certain actions, however achievements are not available out of the box.