A "Thank you" post can help make the day of the user that helped you, but what about saying "hey, this is the best answer of this topic!"? This new feature will let the user know they have helped you out and give an easy way for someone else who may have this issue locate the fix faster.
To mark a post as the "Best Answer", just click the check mark in the right side of the post.
After you confirm the action, the post will have a green background and a "Best Answer" badge.
When you mark someone's post as the "Best Answer", you don't only make the helpful user happy but also tells the community that the user is indeed capable of helping other users.