Proposed resolution (November, 2010) [SUPERSEDED]:

Change 5.13.9 [lex.ext] paragraph 1 as follows:

If a token matches both user-defined-literal and another literal kind, it is treated as the latter. [Example: 123_km, 1.2LL, "Hello"s are all user-defined-literals, but 12LL is an integer-literal. —end example] The syntactic nonterminal preceding the ud-suffix in a user-defined-literal is taken to be the longest sequence of characters that could match that nonterminal. [Example: The ud-suffix in 1.0e0X is X, not e0X; in 0x1DZ, the ud-suffix is Z, not DZ. —end example]