3.1 - Can any string can be a term?

[azaroth42]

Terms are case sensitive and any valid string that is not a reserved JSON-LD keyword can be used as a term.

I don't believe this is still exactly true. For example IRIs cannot be used as a term other than for themselves, and strings with a : in them are now treated as prefix:suffix. And what did we end up doing about error vs optional warning for terms beginning with '@'? Also ... empty string is a valid string, but can't always be used as a term?

[azaroth42]

Should reference 9.1 - https://www.w3.org/TR/json-ld11/#terms