With
"symbol-placement": "line",
"text-offset": [0, 0.5],
"text-size": { "stops": [ [ 12, 5 ],
[ 15, 12 ],
[ 20, 30 ] ] }
at
https://map.atownsend.org.uk/vector/index.html#15/51.61316/-0.86409
not all of the footpath names that are present actually appear. Zoom in and they do. They are supposed to appear from vector zoom 12.
Possible factors include name length and the Maplibre GL issue that can make text look "bunched up" against a non-straight line.