This is mainly because of comment spam. I have to put in a human test (the one with the words to select) to make sure that spam bots cannot post comments. I can either put that test before each posting, which would be a nuisance, or I can put it before the registration, so it happens only once, but then I have to require registration before posting. That's how I'm doing it now.

Without such protection I'd have to check the web site several times a day and delete spam comments posted by spam bots. But even so I have to delete spam comments posted here mostly by Indian and Chinese boys who get a few cents for posting comment spam. I have recently changed the rules such that comments that contain links require approval by me before they become visible. Comments without links are instantly visible.