Brion and I are both against the use of boolean parameters in public interfaces, since they severely impair the readability of calling code. This is documented at Manual:Coding conventions/PHP#Functions and parameters. The $withNamespace and $withSection parameters fall under this restriction.
Topic on Talk:Requests for comment/TitleValue
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Ok, will amend.
You may want to consider mutator chaining, like in Message.
Hm... you could use a mutator to strip the section, but not to strip the namespace - there is always a namespace.