How do they find out the alt accounts? Do they have access to IP address or using some other means?
It is probably everything about quality of posts. But for sure they have access to IP.
I have seen one script which is calculating quality of your posts. I think if quality is good or better they woldn't ban you.. but i'm not sure. So maybe better ask some moderator about that.
On this website you have calculator: http://www.bctalkaccountpricer.info/
Does anyone know how do they calculate quality of posts? I don't think that they just count symbols, right? But how then?
propably only the lengh, because there is no software that can do that, it's heavily subjective
they can do in this way, check if the post is on topic, by comparing it to the title, and check if is a reiteration, in the most simple way, by comparing it to all the other post of the thread