SHOULD/MUST fragment identifier definition question

A question to supporters of SHOULD/MUST:

This is to be found in the terminology section:

for MUST:
http://dvcs.w3.org/hg/WebID/raw-file/d21603d3972a/spec/identity-respec.html#terminology
[[
A WebID is a URI with an http or https scheme, which contains a  URI fragment identifier (i.e. a #id ) and which uniquely denotes an Agent (Person, Organization, Group, Device, etc.). The URI without the fragment identifier denotes the WebID Profile page.
]]
should the text contain a MUST there, or is the above strong enough?

for SHOULD:
http://dvcs.w3.org/hg/WebID/raw-file/http-hash-uri-should/spec/identity-respec.html#terminology
[[
A WebID is a URI with an HTTP or HTTPS scheme which uniquely denotes an Agent (Person, Organization, Group, Device, etc.). This URI SHOULD include a fragment identifier (a string after a "#" character).
]]

Does a hash URI require a string after the hash character?

Facebook for example does not have such a string as you can see here:

  curl -H "Accept: text/turtle" http://graph.facebook.com/bblfish

Also is the terminology section the normative one?

  Henry

Social Web Architect
http://bblfish.net/