Zedd do you mean the markdown >, the bbcode [quote] or the @mention syntax?
Each will have a different method. Removing the bbcode is probably the easiest, there might be a method on the $configurator->BBCode object to de-register a bbcode. Alternatively you can disable the bbcode extension and then use a custom or local extender to only load the bbcode you want. Mentions can be disabled by disabling the extension with the same name.
I'm not sure individual markdown blocks can be disabled without re-writing the Markdown parser.
