Sometimes there are people sending "*****bank",etc,
is not it a violation of the rules to have multiple accounts?

No. You are allowed to have more than 1 account, usually people also have their own bank account. FYI you aren't allowed to join in any contest in Bitsler with your other account
You are only allowed to have 2 accounts (usually a normal betting and a "bank"). It's stated in their terms and conditions:
14.2 -ATTENTION:Having more than 2 accounts is strictly forbidden. If u are found to be in violation of this rule all of ur accounts will be blocked and any funds in them will be forfeited.
This is probably to limit faucet abuse from multiaccounters if it exists, and to discourage people trying to cheat giveaways by hiding a second account. Also, if you have 2 accounts, you can't chat with both at the same time, probably so you can't get rain on both accounts.