I disagree that SEO is not part of (web)development. SEO has a major influence on (web)programming style and practices. It's not only a webmaster's concern, but also the programmer's concern. Also, for "normal" programming languages like Java/C#/PHP those kind of semi-subjective "What's the right way?" questions are pretty often asked and tolerated.
However, some questions like the linked one doesn't have much to do with (web)programming. Real programming-related SEO questions should be allowed on SO. All with all, it depends purely on the whole question context. It's not only the "SEO" tag which should be focused on.