Paragraph block: inline styling for mark elements stripped out

[KokkieH]

Steps to reproduce

1. Create a post
2. Type some text in a paragraph block
3. Edit block as HTML, and wrap some text in <mark></mark> tags.
4. Add a style attribute and set a custom background color
   Example: <p>This is <mark style="background-color:red;">some</mark> text</p>
5. View published post
6. Leave the editor and then open the post again for editing, and check HTML

What I expected

For the text to be highlighted in the custom color I'd added in the style attribute.

What happened instead

On the published post the text is highlighted in the default yellow color based on the browser's built-in styles

On leaving the editor and reopening it, the style attribute has been stripped from the mark element.

This issue appears to be specific to WordPress.com - on a self-hosted WordPress site this works as expected, so I'm guessing this might have to do with the safe-list we maintain for what HTML tags and attributes can be used on WordPress.com, rather than an issue with the editor itself, so this is more of an enhancement request than a bug report - until text highlighting is natively added in the block editor, can we at least ensure that WordPress.com site owners can use all the HTML tags and attributes that allow them to do this manually?

Context / Source

Discovered while testing a solution for a user question in https://wordpress.com/forums/topic/redacting-text/.

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[inaikem]

Scrubbed request. I have confirmed the style attribute is removed on Simple sites but retained on Atomic and self-hosted sites.

I expect this is intentional - especially on Simple site plans which don't permit custom CSS.

@simison, can you see the use of style in the code editor ever making it to Simple sites?

[simison]

Yes, we will need this for WordPress/gutenberg#34680

I gave Team Calypso heads up earlier this week. Cc @fullofcaffeine

[inaikem]

Thank you!

[KokkieH]

@inaikem

I expect this is intentional - especially on Simple site plans which don't permit custom CSS.

We've never blocked the use of inline styles on free sites, and it works for, e.g. <span></span> tags.

[KokkieH]

This has been fixed in D68544-code (also related to #57036), so closing this issue.