It appears that the "Thread:" hyperlink contained in these forum email notifications is incorrect, at least in one instance.
The post that started this thread has message_id=238612. However, the Thread: hyperlink in the email of the post has message_id=238610. Launching a browser on the link results in a "there was a server error processing your request" message.
This is the only message (I've checked several, including the first in another thread) that seems to have this problem.