I found a new limited social networking site called Postwaves today.
It apparently allows posts to stay on its site if other users vote to keep them there, as a way of controlling spam, gratuitousness and fake news.
I then looked up one article, from Space, about life in a research station in Utah preparing people to live on Mars, here. That site presented an annoying popup (about Trump and infrastructure, good enough) that wouldn't go away until I went into the article again.
I saw another article with a basic biology lesson on genetics. Another article, about concussions among high school football players, had disappeared.