After the 554 hard-bounce bug fix, I noticed four consecutive group-activity log entries on the same day (Feb 1) for the same member, with no intervening unbounces for that member. The member's email delivery history showed monthly bounces for the group guidelines, which is sent as a special notice, and she is a special-notice member. Three of the entries were on Feb 1 and the fourth was on Feb 4.
I believe (but am guessing and not 100% sure) that one of the log entries on Feb 1 was from a bounce of my group's guidelines, that the other two entries on Feb 1 were from bounces of group guidelines two other groups she is subscribed to with special-notice-only, and that the bounce on Feb 4 was a bounce of either a special-notice that went out from a fourth group she's in and is subscribed to via special notice, or a bounce of a regular message from a fourth group she's in and subscribed to via individual message. (I would guess the latter, since she only appeared as bouncing at all after the 554 fix.)
If my guesses are correct, the solution is a simple "if" statement that conditions sending of an "xyz is bouncing" log entry to any particular group only if the member is not already categorized as bouncing in that group.
Messages are the sole opinion of the author, especially the fishy ones.