I'm not sure I understand the issues. Does your browser start lagging when trying to insert huge chunks of text? Do you have JavaScript enabled? If so, there is a fix coming soon™, where the editor will be replaced with a more robust and less laggy one.
If I understand the other issue correctly, the <>
code does not work, because it is seen as an HTML tag and those are escaped. This is due to the fact that allowing these characters is a security issue.