My question is that, if someone doing bounty without spamming the forum . His also has intentions to make good post as much as he can. Does this effect his reputation.
According to your post title you are asking bounty will effect on merit or reputation.
Just I want to clear one thing, merit and reputation is totally different. If you just joined on forum and doing bounty campaign than how you expect merit on bounty post. If you made useful and high quality post than obviously you will earn merit even you are doing bounty. But lot of reputed member discourage to send merit for bounty hunters.
Now come to the reputation, if you have reputation than there is fair of lose. If you aren't reputed member's on this forum than why you worried about it ? You can see me I am a high merited member but I am not still I can't say I am a reputed member for forum.
Bounty campaign and signature campaign is different. Even you are reputed member than signature will not effect on your reputation. Because reputed member can't be spammer. Even I believe doing bounty also not effect on your reputation if you are not promoting scam project.
As I told you, merit might be effect by bounty report for newbie. Because merit depend on sender mind. It's true that lot of reputed member avoid bounty hunters.