Well, it is legal to own multiple accounts here on bitcointalk, but it completely depends on what you're intentions are. One valid reason is in the case of
DarkStar, a well known signature campaign manager here on bitcointalk. Well, his job as a signature campaign manager requires posting a lot of short messages when answering questions, so instead, he created an alt account,
DarkStar_alt, to answer those questions for the campaign. Not sure if that was the exact reason why he made an alt, but you get the idea. If your intentions is to use the alts to join other campaigns, then you'll be banned from the campaigns.
I was also confused about that, is it possible to create more then one account from same ip address on Bitcointalk forum ? But I got the answer suddenly today. Some one was post about it. There are reply by forum moderator and DT member's. Yes we can use multiple account from same ip address. But basically it's not good unless your account has bad or lock. Reference is below.
Don't fucking do it Idiot, multi accounting is a quick way to get tagged with negatives and make all accounts associated with you tagged with red paint..
DO NOT LISTEN TO OP HE IS A PRICK
multi accounting is frowned upon by the forum.
Wow calm down.