I can see the post when I go directly to it (with either the kbin.social or artemis.camp account), but it does not appear in my threads area under my kbin.social account (the one that posted it).
I'd gotten a 50x error page when trying to submit this post, too - but it went through anyway? This post doesn't show up in my threads page, though.
I read back your earlier comments before I tried posting - I know you have other pressing matters on your plate. As you can see, I just created this user at artemis.camp, so that I can get those notifications ... maybe?