So looking at notifications (I'm on a Mac running Chrome), I can right-click and open a new tab when I click on the title of the post, but not when I click on the header (the "new post in" or "your post stacked" part). In the case of comments, I can right-click on the title, but not the comment itself (where, admittedly, I'm more likely to click at first). So it does seem that all posts can be opened in new tabs from notifications, just not from all points. Not sure if this was the case before the recent update.

https://i.imgur.com/ANCrFyU.png https://i.imgur.com/9iauQEa.png