Comments: Add a filter to allow comments on draft posts

[SainathPoojary]

This PR introduces an allow_comment_on_draft filter to wp_handle_comment_submission().

Currently, comments on draft posts are hard-blocked. This filter allows developers to override this behavior by returning true, enabling use cases like internal editorial workflows and pre-publication discussions. The existing comment_on_draft action is preserved inside the conditional logic so it continues to fire when comments are blocked.

Additionally, the pre_comment_on_post action has been moved outside the final else block so that it fires unconditionally when no error is returned, aligning with the intent of the original patch.

Note: Based on recent Slack discussions, the allow_comment_on_trash filter originally proposed in this ticket has been omitted due to unresolved architectural questions around how comments on trashed posts should interact with wp_trash_post() and wp_untrash_post().

Trac ticket: https://core.trac.wordpress.org/ticket/19739

Use of AI Tools

AI assistance: Yes
Tool(s): GitHub Copilot
Model(s): Claude 4.6 Sonnet
Used for: Edge-case checks, and assistance with the PR description; implementation and testing were reviewed and verified by me.

---

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props sainathpoojary.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

Test using WordPress Playground

The changes in this pull request can previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time the link below is clicked.
• Every time this pull request is updated, a new ZIP file containing all changes is created. If changes are not reflected in the Playground instance,
  it's possible that the most recent build failed, or has not completed. Check the list of workflow runs to be sure.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Test this pull request with WordPress Playground.