Allow Re-threading of comments

[MattyRob]

Users who comment on posts sometime miss the 'Reply' button and add a comment using the comment form at the bottom of the post even though they are really replying to a previous comment.

A neat feature would enable an admin level user to re-thread such comments as children of previous comments and as such re-thread the comments.

This would improve readability of posts with lots of comments that get 'out of thread'.

[solarissmoke]

#16252