You should make it possible for a user to delete topics that is made here, i have just made one that i found the answer to, my own error. Topics like that just take up place for real topics.
So besides the possibility of editing the topics it should be possible to delete them as well. :-)
I don’t think you can delete a topic you made on the nopcommerce official website as it is, but this feature would be nice to have. Sorry, at first I thought "Forum Subscriptions" would allow you to delete a topic you made but it looks like that is for deleting subscriptions to topics that you ask to be notified by email on :) I think it would also be nice if you could edit the titles of the topics you make.