May Coinmerce just block and/or terminate my account?

Yes, Coinmerce may, although not just like that, block and/or terminate accounts. The blocking of an account may be temporary in order to perform checks or investigations, but may also result in the termination of an account. What will be done with the crypto assets in the account will be determined depending on the circumstances of the blocking or termination. If the account is closed because the user is receiving funds from gambling sites despite warnings from Coinmerce, the cryptos are usually sold and the funds will be returned to the user. Coinmerce also closes an account if it appears that fraud is involved. In that case, the funds are often frozen.