make nickm's proposed convention from 2003 be gospel

doc/HACKING

@@ -312,11 +312,11 @@ operation.
 If a library function is currently called such that failure always means ERR,
 then the library function should log WARN and let the caller log ERR.
 
-[XXX Proposed convention: every message of severity INFO or higher should
-either (A) be intelligible to end-users who don't know the Tor source; or (B)
-somehow inform the end-users that they aren't expected to understand the
-message (perhaps with a string like "internal error").  Option (A) is to be
-preferred to option (B). -NM]
+Every message of severity INFO or higher should either (A) be intelligible
+to end-users who don't know the Tor source; or (B) somehow inform the
+end-users that they aren't expected to understand the message (perhaps
+with a string like "internal error"). Option (A) is to be preferred to
+option (B).
 
 Doxygen
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