@julian
.header .header-topic-title {
display:none;
}
???
But in all seriousness, it seems like something that wouldn't really be missed. On mobile you only see 14 characters of a title anyway, and on desktop you've got the title of the topic in the tab, and on the address bar. Plus in terms of SEO, it doesn't really help nor hinder as it only appears when you've scrolled down the page, so the SEO would come from the title being to the right of the avatar, or even from the breadcrumbs.