That is how it (often) goes. Nevertheless, one of the non-written rules is not to ask/beg for merit. Its actually rather counterproductive to do so (or at least you need to be a bit more subtle about it).
I'm just a little curious about this issue, what if these people know each other, they often give each other merit? How to prevent abuse. It is like asking for merit 
How to prevent? It's up to you whether you abuse it or not. You can freely commit but make sure you are ready to face the consequences huh
. So do not attempt to do it at all or else your accounts will get in trouble. Even how hard you try to alibi, both of you are abusers in the eyes of veterans here especially if you are just a mediocre poster.