Right, the comment system should now be working, I didn't realise it wasn't (i.e. it worked fine on my initial tests).
Looking closer, the lack of properly escaped characters meant that many comments failed to be written to the database and just resulted in an error message.
Apologies if you tried to leave a comment only to get an error.
As I said, should be working okay now, drop me a line if you're still experiencing problems.