Preserve threads where the parent comment was deleted
Problem to solve
Currently, when you start a thread on the merge request "changes" tab, or when you start a thread as an issue or merge request comment, then delete the comment that started the thread, the child comments get realigned to a new parent (the second comment in the thread)
This is a problem because the context of the discussion itself is changed. If the discussion has started due to a particular comment, and that comment no longer exists, then the child comments become somewhat irrelevant. For example:
| Before deleting the parent | After deleting the parent |
|---|---|
 |
 |
The context in the above examples has now changed drastically and we are no longer being transparent about the original discussion.
This has recently come to light with the new releases from the merge ref comparison mode epic, particularly because we still need to handle this circumstance when comparing against merge(head). The proposal on that issue is currently to keep the functionality the same as it is today, but we should instead evaluate whether it is correct today.
As a user, I want to see that there used to be a different parent comment on a thread, so that I can understand the context of the children comments.
Intended users
User experience goal
Proposal
@andr3 has proposed a valid option, which is to keep the parent comment in tact, but remove the user data, and change the text to indicate that it's been deleted:
