Composition is current (top left), space fixed (bottom right), value fixed (top right)
The text-shadow for mw-echo-notifications-badge has an invalid value, as a result the style is ignored and not rendered.
The value is invalid because it contains a non-breaking space, which is not allowed.
The value is also missing a leading 0 (it should have 3 dimension values, 2 works (as demonstrated in the screenshot) but is probably not what you want).
See attached screenshot for:
- Current value, and rendering thereof (no shadow because value is invalid)
- What it would look like with the space fixed (0 1px shadow)
- What it would look like with the value fixed (0 0 1px shadow)