I never said having multiple account are not allowed (unless used to farm campaigns)
I was trying to say that no matter how many accounts he registered, it won't be able to post anyway since his IP got Blacklisted, maybe I should put a better effort on my wording next time

It's also depends on his ISP, some use dynamic IP, which if the modem are restarted it will automatically grab a new IP.
Ah. I was attempting to quote just OPs response for that but my phone couldn't cope with it - so I scrolled over what you put and considered it was his so it did seem a bit confusing.
Also, routers do change when using dynamic IP assigning. They usually have to be off for around 8 hours is normally the suggestion as the ISP will tend to try to assign the regular IP back to the same router again if it hasn't been taken (my suggestion: turn it off as you're about to sleep in the evening and then turn it back on in the morning and it should get a different IP - though the process may need repeating).