But before I give karma, I clearly see he has 1 karma. But after I sent 1 karma, why did it become zero? 
He probably had -1 karma. He spammed in several topics yesterday and lost several karma. admin even gave him -5 karma for low quality posts. Last time I saw his account yesterday he had 0 karma. So I guess later he got -karma for one of his meaningless posts additionally. So when you gave him +karma his result became 0. 
It seems I like the system on this forum more and more. That is, when we make mistakes such as making spam posts and the like and we get -Karma then we can fix it by changing our posting habits for the better. And -Karma will disappear when someone starts to judge our posts as useful. Karma becomes like an indicator of a user's quality. And about users whose Karma becomes Zero means that they have improved their posts to be better so that -Karma starts to decrease and finally disappears. This is very interesting.

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I just karmared you because i have similar thoughts in mind because have been getting some karma as well but there is no way one can detect who they are from and what post received the karma i guess we just keep making good contributions and that will be our reward for the contributions.
It will be good if one is able to see what post receives karma and from whom at least but if thats how the forum as always been then i think we just need to adapt to the system.
Thank you friend. It seems like many people have questions about this. Because the more people are interested in something, the more questions they will ask to get to know that something better. And now this forum is starting to be liked because all users are starting to get used to this forum. So don't be surprised if there will be lots of questions related to this forum.
But now I am starting to understand that this Karma system is also the best as it is now. Because this can be an important indicator for assessing an account. And now I'm also starting to think that I shouldn't be stingy in giving Karma to every user who impresses me. Because Karma stock will not run out

+1
But I will start by adding a ''+1'' to every post that I appreciate Karma. To appreciate the user. So that users know which posts managed to amaze someone. Because what I feel so far is that every time we get appreciation, the motivation to be better will grow bigger. So that our quality can continue to improve thanks to this motivation.