Options clauses on procedures split correctly. An options clause (WITH EXECUTE AS …, WITH RECOMPILE) ends the header too and stays with the definition.
Comments before a module’s CREATE no longer derail the split.sys.sql_modules stores the batch as written, comments included; the leading trivia is now stepped over before the header is matched, for routines, views, and triggers.
A parameter list ending in a line comment renders intact. The closing parenthesis is printed on a new line rather than being swallowed by the comment.
A parameter-less procedure renders without parentheses. T-SQL rejects CREATE PROCEDURE name(); the empty list is omitted (functions keep theirs).