Assume that users have the ability to edit their own comments. Or administrators can also do that.
Do comments have revisions like posts and pages? If so, how would you access those revisions?
The "History" link on the admin/comments page does not show any editing/changing/updating of the comment, whether done by the admin or the original commenter.
If no comment history is available, how would I add that capability via a filter?
Added for clarification
In regards to the 2nd question that was looking for a starting place for adding comment history (which might have been better to post as a separate question):
I agree with answer comments that creating comment history looks like a big effort.
On the site, I use a plugin that adds "spam/delete/trash" links next to the 'edit' link that admins see. Each of those choices does the action, as well as removing the comment from view. There was a request for a 'redact' link that would replace the comment text with "[redact]", as the requestor wanted the comment text to be removed, but show as redacted.
Then there was the thought that there might be a reason to 'un-redact' a comment, restoring the original comment content. So was looking for a way to do that similar to post/page revisions.
But agree that adding comment revisions would be a big project. Maybe changing the status of a comment to a new value (not spam/delete, etc) and modifying the comment_list to replace the comment text with 'redact' on display, but not modifying the actual content.