Is there any way to manually delete your own topic, or do you have to go through mods for that? Because I'd really rather just get rid of the thing altogether, but for no reason other than a whim.

No, users can't lock or delete their own topic. You can have your topic locked by pinging the corresponding minis for that board, but I doubt they'll delete it.

topics are only deleted if they are crazy offensive, or if there's a huge amount of spam flooding the forums, extreme cases like that.

Tragic...but oh well. I could always edit it into a more functional topic some day later, I suppose.

I think that you can have any of your own topics locked at request... I don't know about deleted