TIMTOWTDI - or some such acronym. Looking at the source for sp_helptext, it's pretty well just grabbing the syscomments:
SELECT text\nFROM syscomments \nWHERE id = OBJECT_ID(@objname) and encrypted = 0\nORDER BY number, colid

Since it's a question of tools, though, I'd want to know what's actually in the underlying tables, stripped of any intermediate facilities (including stored procs). And I'd want to see that raw value in the same tool that is causing the grief.