I'm not familiar with Discourse, but it has to be better than Disqus. That's a trainwreck.
Unfortunately, the person or people at Adobe who convinced the higher-ups that Jive is worth using, didn't disclose the fact that Jive cannot be exported/migrated to anything else (never learned why) so every thread and post that has been started since Jive went live can't be retained. If they switch to something else, everything will be lost.
UPDATE: I take that back. I actually have a Discourse account, but can't remember my login/pw for it. I looked at it years ago, and completely forgot all about it. YES, it would be much better than Jive.
You should have been able to delete the whole thread, yourself, since you were the one who created it. Even with a few replies, you should still be able to delete the whole thing. The delete button _should_ be up top on the right hand side.