How do I remove this blue border on homepage and category topic lists?

Development
4

It’s a temporary indicator you’re focusing on a topic. That’s not quite the same as hovering or visiting a link. EDIT: as CoinCoin and Jake stated below, it’s useful for accessibility and on mobile.

You can hide it with CSS. Add this to your theme or theme component:

.topic-list .main-link.focused {
    box-shadow: none;
}