Deleting Parent comment makes children comments "unreplyable" and not editable

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Describe the bug

Not sure if this a bug or by design constraint: When a comment B is a reply to a comment A, and comment A is deleted, it becomes impossible to reply to comment B. When you try, you get this error.

The response is

{
    "ocs": {
        "meta": {
            "status": "failure",
            "statuscode": 404,
            "message": "Could not create comment."
        },
        "data": []
    }
}

This seems true for any comment "downstream" a reply chain of a deleted comment. If 1<-2<-3<-4<-5 (meaning 2 is a reply to 1, 3 to 2 etc.), if one deletes comment 3, one can still reply to comment 1 and 2, but not to 4 and 5.

To Reproduce
Steps to reproduce the behavior:

1. Go to the comment section of a card
2. Create a comment A
3. Create a comment B as a reply to A
4. Delete comment A
5. Try replying to comment B will cause an error

Further the orphan comments become readonly - when one tries to update them, one receives

{
    "ocs": {
        "meta": {
            "status": "failure",
            "statuscode": 403,
            "message": "Permission denied."
        },
        "data": []
    }
}

Expected behavior

If this is a design constraint, then it would be nice to have some flag that marks broken comments as "orphans" such that the UI can stop offering the option to reply in the first place. The current UX is that simply nothing happens.

Otherwise I would expect comments to remain "replyable" and editable, even when their parent is deleted.

I am willing to dig into that and work on a PR in case there is something to be done :).

Nextcloud version: (see Nextcloud admin page)

confirmed on 26, 30, 31

Signing status:

Login as admin user into your Nextcloud and access
http://example.com/index.php/settings/integrity/failed
paste the results here.

Start by reproducing the issue in the comment section of a card using the A→B→C reply chain described in the report. Check both the reply and edit behavior after deleting a parent, then ensure the finished behavior either keeps orphan comments replyable and editable or clearly marks them as unavailable in the UI.