You are not going to get negative trust for having multiple accounts. There is no rule against it. DT users tag those who misuse their accounts and perform actions they shouldn't. That includes enrolling those accounts in the same signature campaign, meriting your alts from your main account or vice versa, giving yourself fake positive trust, etc.

Having fake conversations and talking to yourself should also be a reason people get a negative tag, but I don't think that is the case. There have been cases where you can observe the same person making a post or asking a question and his alt answers. They do it to phish for merits or increase their post count.