~ to encourage him join the community i explained how he can earning money by joining a signature campaign
I wouldn't call this " joining the community", unless you mean the community of spammers. The sad reality is that the great perks of signature campaigns make many people join Bitcointalk for the wrong reasons.
Totally agree with this opinion. However, we can't deny that pay per post model is successful one to attract a large user base of quality posters. I can guess that many of quality posters today came to this crypto community encouraged by this model especially after implementing the merit system. As a proof, compare bitcointalk to other forums in quality posts after implementing the merit system which has a primary goal to reduce spam and it's successful.