リンク専用カテゴリ？

[Falco]

How can I customise CSS for each category? (as in having different design for each category)

When you’re in a category, discourse adds the category slug to the body element. For example, on meta here when I visit the bug category I get category-bug in the body tag. If you use that as a selector you can style each category differently.

ただし、他のカテゴリを閲覧しながらあるカテゴリに投稿できるため、ご希望通りに機能しません。