Part of #71774
Addresses: #71774 (comment)

What?

This PR integrates two-line comment date displays into one line and displays either the date or a human-readable diff depending on the comment date.

This PR also removes the date from the header of the comment form.

Why?

• The current comment header looks a bit clunky and takes up a lot of vertical space.
• The date is only displayed as a human-readable diff, so you cannot know the exact date the comment was posted.

How?

• If the comment date is less than 30 days ago, show a human-readable diff.
• If the comment date is older than 30 days, show the date according to your site settings.
• Hovering over or focusing on a date will display the full date. This format is the same as the format of the post date label.

Testing Instructions

• To create a lot of comments at once, please use my plugin: https://github.com/t-hamano/block-commenting-data-generator
• Add comments to a block and confirm the date.

Screenshots

Before	After