Thanks. I know about the reverse engineering, but there is no similar use case from the Discourse front-end to intercept. I mean that, while I’m logged in as admin, there is no way to create a topic as a different user.
The workaround I’ve implemented for now is to let the specific category have see/comment permissions for everyone and see/comment/create for admins. Then topics are created by “system” only (so there is no way for users to tamper with the titles) along with a template original post. Then I can use the API key to comment as different users in those created topics.