I don't know if it's something wrong with my account or what but this has happened a few times now. When I add a new post to an existing pool, it gets yeeted from the gallery. Even when no other posts in the pool exist on the first page.

I've seen other pools where the first few posts are fine an then it starts hiding. And I've seen posts that are part of older pools without getting hidden. But I've tried it both via pool now and via parenting and both ways my post vanishes.

And apparently I can't un-parent to make my post re-appear so it's basically banished to the shadow realm. What am I doing wrong?

i un-parented it for you :)

for future reference, to do so you simply set it's parent ID to 0

Thanks. Still no idea how people add things to pools without getting shadow realm'd tho. xD

Posts that have a parent post don't appear on the front page. As far as I know, posts in a pool shouldn't be affected unless they have a parent.
You can always set a post's parent a few days after you post it, so it appears on the front page for a bit.