'I've also noticed that comment spam seems to actually work..'
My pet theory is that with any filter there is always some stuff that gets through and if you're automatically spamming a few thousand comments then even a tiny percentage is going to make it worth the effort.
There is also a chance they'll get a few comments on sites with dofollow links, of which there are still some around.
Dofollow and nofollow don't matter as much as the did a few years ago. It will look like unnatural link building if 100% of your backlinks are dofollow.
There's usually a intial period where sites with zillions of spammy backlinks will rank, then they will crash after a weeks /months and will probably never resurface again.
My pet theory is that with any filter there is always some stuff that gets through and if you're automatically spamming a few thousand comments then even a tiny percentage is going to make it worth the effort.
There is also a chance they'll get a few comments on sites with dofollow links, of which there are still some around.