You’ll be pleased to know that I have calculated a winner! I used the power of mighty MySQL to pull all names from the comments table, group by email (to eradicate duplicates) remove those who could not/did not want to enter and randomise the results. Everyone was assigned a number and I save the output as an HTML file (which you can see here.)
I asked the random number generator to give me a number between 1 and 123, and was given 24. That means that Annie (comment is here) of ikillhearts is the lucky winner! Congratulations Annie, I will be contacting you shortly with details of how to claim your t-shirt.
Thank you to all who entered — I got more interest than I expected and the rush of comments in one go led me to discover a few badly optimised bits of code (thanks MySQL max_connections) in my system. Nonetheless it was interesting, and I hope to do it again some time.