I've just removed categories as a thing from my website. I'm still using tags on all the content, but categories no longer exist. This is for a few reasons:

• categories are not Microformats2 markup-able (as we can't distinguish between tags and categories, it's just p-category which we use for tags)
• categories in the site are not currently hierarchical - although they may be defined as such, they're not presented like it
• categories are not any more meaningful than tags, as they're almost always the same, or a reduced set, compared to the tags

So we may as well just remove support for them, as they serve exactly zero purpose.