Does it matter who reports someone or if they report often to almost never? Does anything effect the validity of the reporting action? I would assume not but I would like to know for sure.
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Report away. You can't get banned from reporting too much or too little. The system has controls to prevent abuse, but these controls do not affect users. You should report for anything you think needs reporting, you don't have to consider how it will look. The moderators can't even tell who reported something, for example.