Last month I asked: Should I be worried about how fast I use the site?
I'm pleased to announce I got my first captcha.
This is just a feedback, for perhaps altering the algorithm behind it if at all possible.
What triggered it is opening two bookmarks at once, both are search results, one of which is
is:a created:2d.., which is sorted by new. My rationale for that is here.
Update: I was able to reproduce it. Middle-clicking the folder with the 2 bookmarks brought up the captcha for the second tab.