I don't know? Can you delete your first post? Can I delete my reply? I'm going to try. There might be a difference between "first post" and "replies".
well, here goes!
EDIT: I didn't complete the operation but it seems that I could have deleted my (this) reply. I clicked that "3 dots" control thingie and was presented with options to "delete", "edit", etc. I proceeded far enough along the "delete" function that it confirmed "are you sure you really want to delete your post?" at which point I bailed.
EDIT # 2: I added another reply and I was successful in deleting it. Still unknown if the "first post" can be so deleted. I'm a bit shy about starting a new thread just for testing.