Yesterday, when I logged in I noticed that there was an 'Alert' advice waiting for me. But, trying to go to that link showed that I hadn't permission to view. It appears that it could have been generated falsely, as there is no indication who responded to my [original] post in that thread. Now I have just logged in a short time again, and I have another 'Alert' prompt which I can link to, so that was OK.
A reply to the thread had been removed as off-topic. By the time you logged in, whatever was linked in the alert was no longer available to be seen. (Removals apparantly do not cancel pending alert messages.) So, I think it makes some sense.