I posted a question on askubuntu, unfortunately it was a duplicate of a previous question (I did search, sorry!). However, I came back a few times over the next few days to check the homepage to see whether I had any inbox messages informing me of any answers or comments on the question I had asked. As there were none I assumed it hadn't been answered.
Eventually I went to the page of the actual question to see that it had been marked as an exact duplicate, which is fine but would it not be helpful to have a message sent to the question-asker to inform them their question has been marked as a duplicate?