Description

If I add a left border to a site when using an RTL language, it also adds a black right border.

Step-by-step reproduction instructions

1. Using a site in an RTL language
2. Open the editor and add a block that can have a border
3. Apply a left or right border (these controls are backwards, see Split border control UI is backwards on RTL sites #44171)
4. Only set the width and/or color, don't set the style
5. See a border appear on the opposite side, no color applied
6. Add a style, the border appears, but the opposite border is still there

Screenshots, screen recording, code snippet

Here you can see I've added a 2px orange border, but only this larger black border appears.

When I add a style, my border appears, but the black one stays there.

Environment info

• WordPress 6.1-alpha-53929
• Gutenberg 14.0.3
• Mac + Firefox 104

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

No