You can enable specific HTML tags (like <i>
, <b>
) in TextFormatter using a local extender. But all these effects can already be achieved natively with BBcode or Markdown.
If you are talking about arbitrary HTML including inline CSS, iframes or even javascript, this has been discussed many times on the forum already. This would be fundamentally unsafe, and the mechanism to restrict access to such a feature would make an extension quite complex. There are usually simpler and safer ways to achieve the desired goal.
Can you describe what your use case is and which tags do you think you would need to achieve it?