I hope to load and browse the tiddlywiki forum in my own tiddlers, but it seems that the website does not allow me to do so, or my embedded code format is incorrect
That’s right. It doesn’t allow this. Discourse sets the X-Frame-Options header to SAMEORIGIN, which means that it cannot be included in any iFrame, unless that’s served by the talk.tiddlywiki.org server.
If you really want to pursue this, you might check with the core team whether that setting is overridable in our installation or if it’s just how Discourse works. My guess would be that we can’t override it, but I’m not a Discourse administrator.
Okay, maybe there will be a better solution in the future. To be honest, I’m a bit lazy. I don’t like to switch web tabs back and forth, but prefer the all in one style. So now my tiddlywiki is almost becoming an operating system