For anyone who sees this, I’ll better clarify this statement: “Best practice is to allow the browser or theme to define the outline weight and style.”

The reason for letting the browser define the color is that Chromium-based browsers use a double color (blue and white) outline that works on both dark and light backgrounds. There are a lot of websites that have defined the color in their styles, as you may see if you were to look at my website. It’s not that this is not OK, but if you set a color for the focus outline, then you have to do a lot of work to define it differently in different sections of the website (like on my site it’s blue over white backgrounds and yellow over dark backgrounds). This works OK for a custom theme, but from a plugin standpoint where you have no idea what the background color of the site will be, it’s safer not to have a color.

You could set the weight and style if you want, but I would stick to 2px solid. 1px dotted will be really hard for people to see.

Generally, from a plugin dev standpoint, I’d think of the focus indicator as something the theme should control, so I would leave it out. Or maybe intentionally define it for themes that have failed to do so.

But removing it is problematic because it overrides the focus indicator set by the theme (assuming there is one), and then someone has to add CSS with !important to get it back.