Currently it seems that posting annotation to a PR using the Code Insights API, works only when the annotation is on the same line as the code change.
So if we imagine that there's a PR with a change on line #10, we can post annotation on that line. But if we try posting the annotation on line #8, the API returns 204, as if the call succeeded, but no annotation will be visible on the PR diff view.
Is that expected behavior or am I missing something here?
Edit:
And now I've found the actual API doc, which explicitly says that annotations outside the diff will not be displayed. https://docs.atlassian.com/bitbucket-server/rest/7.18.2/bitbucket-code-insights-rest.html#idp10
You may remove my post.