Board Thread:Support Requests - Getting Technical/@comment-11413557-20140222003322/@comment-1330470-20140224172549

Runescape Wiki has the characteristics of being a Very Large Wiki, and of being very well maintained, both of which lets them get a little bit more leeway.

The three-custom-namespace rule is probably more of a guideline. If you can demonstrate that you definitely need these namespaces, and would maturely use them, I am sure that the limit could be exceeded. The rule/guideline is probably there to deter overly-zealous founders of wikis with two pages thinking their wiki requires seventeen custom namespaces that they obviously will never utilize. Runescape Wiki, on the other hand, makes clear use of their custom namespaces.