Zé Fontainhas has written a post that needed writing, and we need to read it. Too often, we pre-judge people's capabilities based on false assumptions.
Being a contributor to non-developer centric aspects of WordPress doesn't make someone not a developer. Also, talking a lot about development stuff doesn't guarantee a developer's skills. Even moreso, skills with certain types of development are not the only metrics of a developer's abilities.
In Zé's more eloquent words:
What is really, really annoying are the assumptions, a disease I see rampant in the WordPress community at large. A disease that fosters the calcification of perceived skills on the one side, and which cements a false sense of authority on the other. It encourages people to say of you “He’s a (this or that)”, and, even worse, it encourages you to describe yourself as the “master of (this or that)”.
Success is first of all a factor of skills prior to WordPress, really: a commitment from the board, an adult planning and follow-up, and a competent team that doesn’t shy away from asking and learning, among many others. It goes without saying that all other skills, prior to those, are a given: manners, grace, humour and patience. And, of course, the least common of skills: common-sense.