Wordpress failed, mostly because I can't drop whatever I'm doing at the time to find out why an update isn't installing. And if you don't install updates, Wordpress gets hacked. When you get hacked, link spammers load up your pages with link spam. I've no time to participate in this arms race, so I switched to Habari.
The thought behind Habari was that it wasn't as popular as Wordpress, so maybe it wouldn't be as much of a target as Wordpress. Wrong. Not long after I installed it, new comments would be loaded in every 3 minutes. Simultaneously, Habari experienced a failed login attempt a few times every minute. Somebody was trying to get in by brute force.
Rather than wait for the brute force attack to be successful, I simply switched to a hosted solution. We'll see how Squarespace goes.