I see the situation differently. Even among expert developers: there are those of us who are good at certification test taking and there are greatly skilled individuals who are not; there are those who can come up with creative code solutions and those who need the solution defined before they code; and those who can do the job in 200 lines of code vs 1000. And, there are many expert developers with no customer service skills. My point is: you have to differentiate yourself. The less talented who self-title get found out.

Back to the client: certifications or not, a person who develops a site is a developer – no matter the knowledge of script language. If they can make WordPress sing they can deservedly call themselves whatever they want. In recognition of coding knowledge there are descriptive titles in use already. If you use WordPress as an application development platform, you are an “Application Developer.” You can be a “PHP Developer” or “.NET Developer.” Add “with XX years’ experience” if need be.

In the long run, the titles and certifications don’t mean much. Proven experience and the ability to satisfy a client does. If people are using a title that you think you should own and if they are also taking work away from you, then they are differentiating themselves by other means than just calling themselves developers, experts, etc. A certification may get a little extra notice but clients want to see what you have done. Use references, build a portfolio, list and demonstrate the widgets or plugins you built, sell yourself. This situation isn't necessarily a mess.