The list of "pull requests" for the kbin project is here. A developer makes a pull request when they've made some changes to their copy of the code, and are requesting that those same changes be made to the original main code of the project.
If you look at the list of "closed" pull requests, the ones with the purple icon are the ones that have been approved. This is a good way to check how active a project is.
I've heard about this happening once before, though I'm a little fuzzy on the details. I think it had something to with the file getting misinterpreted as an image, and the person was using a userscript that automatically expanded images.
Generally your posts will be successful despite the error, but they'll also end up buried in the default "hot" view. If you switch to "newest" you should see it. Upvoting your own post should make it show up correctly in hot. No idea about the deletion thing though.
I was trying to support @Animemes when I first got here, but ran out of saved stuff a month ago, and the community is pretty quiet now. I even resubscribed to animemes on reddit recently, but they haven't posted anything worth stealing yet. ..
cacheson @ cacheson @kbin.social Posts 31Comments 343Joined 2 yr. ago 
You already moderate 113 communities. I think that's more than enough, and you should stop trying to create more.