Deleted User Comments are deleted

Problem/Motivation

When deleting a user and re-assigning, comments that they have authored are deleted. I assumed that they would be either re-assigned to the selected user during the deletion or at least left to say "Anonymous".

Steps to reproduce

1. Create two users
2. Enable comments for a content type
3. Comment on a node as each user.
4. Delete one user and re-assign their content to another user.
5. Comment on the node from the deleted user will be gone

As a contrast, choosing to delete the user and assign their content to Anonymous DOES leave the comment in place and should show "Anonymous (Unverified)" as the author of the comment.

Proposed resolution

None as of yet. I just needed to mention this as it ended up destroying some data that I wasn't expecting to lose.
I assigned another potentially related issue but I'm not certain that they are related.

Remaining tasks

User interface changes

API changes

Data model changes