There are no rules to use proxies or use any IP, but if you use a well-known IP or VPN with IP banned and you are planning to make a new account here on the forum you can't use the account.
Read this quoted below.
Q: Why is my IP banned? What are those units of evil?
A: Your IP might be banned because it was used by a user that got perma banned. Don't worry - IP bans decay over time if there's not too many of them during a small period. If you register using a banned IP, are using TOR, VPNs or well known proxies, you will have to pay a small fee. This is to prevent spammers while allowing legitimate members to post without many restrictions.
To prevent your account from being ban you must read our forum rules from here
https://bitcointalk.org/index.php?topic=703657.0If you can follow the rules correctly your account is safe.