How do I allow new users to delete (or remove) their own topics?
Just have them flag it, people may be responding allowing an OP to delete is undesirable.
Also note that deleting a topic removes not only the first post, but the entire discussion, which is something you should be averse to doing.
Even deleting a topic with only one post (the first post) is problematic, because topics populate the homepage. If you want to grief a community, create new topics with horrible titles then delete them as soon as a few people see them.
Moreover, people may be in the middle of typing a reply, there is a sunk cost that can not be recovered.
Thanks for sharing your rationale. That makes sense.