On /wiki/Special:EditWatchlist there used to be sections for each namespace, however it appears these are no longer visible.
This especially important for discussion threads because they do not have a namespace prefix in their displayed item, hence the section heading was the only way of distinguishing a page really called "Foo" vs a discussion thread called "Foo" on a larger page somewhere.
In the above, I thought there was an odd main-space page called "Safari 5.1+". But after clicking it I found myself on [[Talk:Compatibility]], not [[Safari 5.1+]].
I believe this is a recent regression. From looking at why it is hidden, I guess this might be unexpected fall-out from the decision to hide "redundant" legend headings on Special page forms.