Post or page (even in Trash) can break listing of category with same slug name

[jorisw]

If a post or page exists with for example slug name "blog", and WordPress's permalinks are set to /%category%/%postname%/ , the post or page will break the listing page of a category named blog.

While this may seem unusual and wrong to do anyway, this persists when the post or page is put in the trash.

A post or page in the trash with slug name 'blog' will stop /blog/ from showing a category named blog. It will show a WordPress style 404, probably it tries to access the trashed post / page instead of going for the category listing.

[markjaquith]

By default, you have to access /category/blog/. We don't support category URLs without a prepended /category/ (or user-defined) slug.

If I'm not understanding you, please reopen with more details.