IDs *not* in selectors

From: http://www.w3.org/TR/REC-CSS2/syndata.html#q4

"In CSS2, identifiers (including element names, classes, and IDs in
selectors) can contain only the characters [A-Za-z0-9] and  ISO 10646
characters 161 and higher, plus the hyphen (-); they cannot start with a
hyphen or a digit...."

So we may infer that #123myid is perfectly legal whilst P#123myid is
not?  If that was the intent, may I request a synthesis of the
rationale?
-- 
Sue Sims