Just to add another point of view. I run a Spanish-language literary community, where users share their creations: poetry, short stories…
We really love the conversation enabled by Discourse, but in our case it is essential that the users can delete whenever they want the topics they create (since they could have some value in terms of copyright). We don’t mind about the conversation being lost, since it doesn’t make sense without the OP.
So I created a (quick and dirty) plugin for that: GitHub - osvid/delete-plugin: A quick and dirty plugin for allowing Discourse users to delete their own topics ALWAYS