That is only done if you are in a topic page where the amount of posts is higher than 20 replies. In that case Ctrl+f is redirected to a search that is scoped

That is only done if you are in a topic page where the amount of posts is higher than 20 replies. In that case Ctrl+f is redirected to a search that is scoped to the current topic and can search it all. Other pages don't have the search hijacked, and of they do you can press Ctrl+f twice to open the browser search.