I think scammers will always do anything for them to gain and earn more and I think they can be reduced bot not blocked. Helping the bounty managers will be a good way to start it because it will be favorable for both sides since lesser participants more earning and give better bounty management for the bounty manager.

Yes, it is annoying.  But I have found solutions to be simple.
Just provide the campaign manager with proof that you are the original owner of the account or information.
All it should take is a couple of screenshots.
I've had it happen to me just once, but it got taken care of after I submitted proof the other person was copying me.

One thing is for sure, there will always be shady people out there that won't think twice about cheating.
No matter what measures campaign managers make, there will always be some new way to cheat it.
So picking a professional campaign manager is essential.
Or, you can always just use something like bountyhive, were they have a great track record and a closed system that weeds out a lot of scammers.

Many scammer on spreadsheet of bounty campaign, they are always participated at many kind of bounty campaign, some time they use our profile bitcointalk for joining signature campaign and many scammer using our article for joining media content bounty campaign.