I think I can still take part in rational debate by embracing the definition of rational truth during that debate

I don't think it will work in this case, because we're debating the very notion of rational truth.

However, I now realise this wasn't exactly the right place to tell about my idea of subjective truth.

I personally didn't mean to give you that impression at all, I apologize if I did. Just because I happen to think that using reason to debate with someone who does not value reason is futile, doesn't mean that I want to actively discourage such debate. After all, I could be wrong !