Probably a combination of mailman "intelligence" and PEBKAC 
In the first: mailman doesn't repeat subject tags, this seems to be
case-insensitive (Looks like I was right - thanks Colm)
In the second: someone is inserting the [ilug] part into their original
post, therefore getting mailman to look on it as a list ID tag.
 Problem Exists Between Keyboard And Chair 
 No offence to whomever is responsible is intended ... all likeness to
persons living or dead, while possibly accurate, is pure coincidence
> -----Original Message-----
>> Just something I noticed yesterday. Every now and then the ilug
> messages come through as [ilug] rather than [ILUG]. This is probably
> the second time it has happened in about 4 months, but I was just
> wondering why it happened?
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