It doesn't link posts to a person, it links posts together as being made by either the same person, or by a grouping of people who have shared the passphase that generates the tripcode.

How can any court prove that you know some random password? And not on any device of yours when it might be a reasonable expectation that you know of it to continue the use of the device, but on some public website? Torture you or subject you to some duress to try and force you to type it in?

I dont think any of that flies.