i need help(very off topic)

[Flak]

Off topic, closing.

[NewEarth]

but different computers have different ip

[darthviper107]

They've got your IP address

[NewEarth]

i made account to some forum and i was there for 1 year and i got banned for no reason,i made new account and i got banned again with description``duplicating accounts is not good idea`` few days later i made third account from another computer and i got banned again ``gtfo *my username here*``
how to they know it was me?how to avoid being banned again?
please dont ban me for this thread,feel free to move it.