If you have a translator, such as Google Translate, then the delete confirmation buttons "yes/no" do not work, try turning off auto-translation and deleting again.
Delete only works within a time frame and if there are no comments yet. I didn’t think quick enough and instead of posting the link twice I’ve edited it to this. Lots of bad decisions on my side. Now it’s also too late to edit.
Oops, sorry, it turns out it's somewhat my fault.