I was just wondering why when you click on stories, events, Duolingo for schools, etc. why it opens a new tab. Just curious. Thanks in advance for answering my question!
The try it out button for the stories on the Lab page has a target=_blank in the link, so it opens in a new tab (normally) but not in a new window as you said.. it makes sense to me that a sub domain opens in a new tab... (don't know if DL is consistent with this behaviour on the whole web page though)
New window or new tab? If it's new window it might be your browser configuration... if it's new tab then it's about right.
As for the reason... no idea. I go with DragonPolyglot's explanation.