When I have a multi-line description (subject + body) the MR title will just be (although possibly truncated) the description. See [this system note](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/164886#note_2087962838) of an example where the changelog trailer ended up in the MR title. Maybe, I'm also using it wrong and I'm not supposed to have multi-line descriptions - but then, what's the relationship between a diff description and the resulting commit message. The use case for this is closely related to the problem I described in #7650 I suppose.