Usually that would be enough, but you have to remember what is spam or an 'abusive comment' or post that doesn't make sense to you might make sense or be completely valid to others.
I understand the fact that what I may find spam, the MODs may not find it spam and hence my percentage is dropping.
However, some members make personal comments/attacks on other users, make bad comments about religion, help others to commit suicide, talk about drugs and so on and I report all those comments but I find that the reports are excluded and so I don't get what can be the reason as they being considered "BAD."
Also, what if half the number of my reports are "BAD", will the MODs start disregarding my future reports?
Well, personal comments/attacks, talk about drugs, etc. are unmoral, but not against the forum rules, so if you report those things, they will be disregarded, as they are not against the forum rules.