I guess it all depends on what you consider a feature. If you look at the community product page you will see many listed:
Tribal Knowledge Base:
Ratings and Reviews:
Of course, you could also include other products such as SMM since it can be tied into the community. I think it would be good to hear a little more detail on your situation and what you are trying to learn so we can reply accordingly.
@trungdien : From my point of view following features will have Good Impact on the Community.
Float Accepted Solutions: https://community.lithium.com/t5/Accepted-Solutions/Float-Accepted-Solutions-below-the-original-post...
Real Time Notifications : https://community.lithium.com/t5/Real-time-notifications/About-the-notification-feed-and-real-time-n...
If my post is helpful and answers your question, please give "Kudos" and "Accept it as a Solution."
Thanks & Regards,