Remove deprecated wellformedweb.org Comment API namespace from feeds

[tearsnow]

Summary

The WordPress feed output still includes the following XML namespace:

xmlns:wfw="http://wellformedweb.org/CommentAPI/"

The domain wellformedweb.org is no longer operated by the original owner and may now point to unrelated or potentially malicious content.

Background

WordPress has included the Well Formed Web Comment API namespace for many years:

xmlns:wfw="http://wellformedweb.org/CommentAPI/"

However, the referenced domain is no longer maintained. Keeping an external namespace pointing to an expired third-party domain creates unnecessary security and trust concerns.

Proposal

Remove the deprecated wfw namespace declaration from default feed output.

Current:

xmlns:wfw="http://wellformedweb.org/CommentAPI/"

Proposed:

Remove this namespace unless it is still required by an active WordPress feature.

Impact

• No impact on normal RSS feed parsing.
• Removes dependency on an abandoned external domain.
• Prevents WordPress-generated feeds from referencing a potentially unsafe third-party domain.

Testing

Verified that removing the namespace does not affect feed generation or comment functionality.

[niki3150]

Remove wfw namespace declaration and wfw:commentRss tag from feed-rss2.php

[niki3150]

I reviewed the code in feed-rss2.php and found that the wfw namespace
is not only declared but also actively used:

<wfw:commentRss>...</wfw:commentRss>

Removing only the namespace declaration would break the XML output.
This patch removes both the namespace declaration and the tag together.
The slash:comments tag in the same block is preserved.

Patch attached. This is my first contribution — please let me know
if anything needs to be corrected.

[siliconforks]

This sounds like a duplicate of #19885?

## Description

Remove the deprecated wfw XML namespace from generated feeds.

The referenced wellformedweb.org domain is no longer maintained.

Trac ticket:
https://core.trac.wordpress.org/ticket/65830

## Testing

Verified generated feeds no longer output the deprecated namespace.

[tearsnow]

For sites that need a temporary workaround before a Core change is released, the following plugin can remove the deprecated wfw Comment API namespace from feeds:

TearSnow WFW CommentAPI Cleaner:
​https://wordpress.org/plugins/tearsnow-wfw-commentapi-cleaner/

It does not modify WordPress core files and only provides a temporary solution. Removing the deprecated namespace from Core would still be the preferred approach.

[mukesh27]

@tearsnow Since we already have #19885, feel free to reopen it or check the comments to understand why it was closed. If you think this still needs to be addressed, please follow up there instead of opening a separate ticket.

[mukesh27]

Duplicate of #19885.

Thanks for the PR!

See my comment https://core.trac.wordpress.org/ticket/65830#comment:5