Should John Smith, XYZ read XYZ as a credential by default, even though John Smith XYZ doesn't? #564

Policy.unlisted_caps_suffixes is off by default because an all-caps surname is a real writing convention: with it on, Jean Pierre DUPONT gives suffix DUPONT. That convention puts the capitals on the family name, either last with no comma (Jean DUPONT) or before a comma (DUPONT, Jean). It never puts them after a comma behind a full name. The reason for the off default therefore does not reach the comma position, yet the comma position is switched off with it:

>>> parse("John Smith, XYZ")
ParsedName(given='XYZ', family='John Smith')                    # no report
>>> Parser(policy=Policy(unlisted_caps_suffixes=True)).parse("John Smith, XYZ")
ParsedName(given='John', family='Smith', suffix='XYZ')          # reported SUFFIX_OR_NAME

Corpus: every corpus file under tools/differential/ holds 3 names with one comma, two or more words before it, and a single unlisted all-caps word after it in mixed-case input (measured 2026-09-30). All three are credentials, and all three put the credential in given today: Ahmad Jayadi, CHA, John Smith, RAI, The Rt Hon Kenneth Clarke QC MP, HMG.

Proposed rule

Rationale: after a comma behind two or more words, an all-caps word in mixed-case input is far likelier a credential than a given name written in capitals.

Statement: in that position, an unlisted all-caps word of three or more letters reads as a credential at the default, reported SUFFIX_OR_NAME. A two-letter word stays as it is today, because it has the same double-surname hazard as #563's dotted initials (Lloyd Webber, AL, De La Cruz, MJ).

Examples (target readings):

"John Smith, XYZ"       →  suffix="XYZ"                            ambiguity: SUFFIX_OR_NAME
"Ahmad Jayadi, CHA"     →  given="Ahmad"  family="Jayadi"  suffix="CHA"
"De La Cruz, MJ"        →  given="MJ"  family="De La Cruz"         · unchanged: two letters
"Smith, XYZ"            →  given="XYZ"                             · unchanged: one word before the comma
"John Smith XYZ"        →  family="XYZ"                            · unchanged: no comma, the DUPONT position
"Van Buren, MARTIN"     →  ?                                       · see open questions

Open questions

• Van Buren, MARTIN (a two-word surname with the given name in capitals) moves under this rule. How often does mixed-case input capitalize the given name and not the family? The corpus has no such row.
• Is this a change to the default, or a third value for the switch (off / after a comma only / everywhere)?
• Should it take the same letter count as Dotted initials after a two-word surname read as a credential: García Márquez, G.J. has no given name #563, so the dotted and all-caps classes stay one rule?

Related: #563, #516.