This is demonstrably not true. Just send mail to an email list that you are on. The email will be sent (confirm with other list members), however you will not receive it when it is relayed to the group by the listserver.
That's actually an incredibly annoying fallout of gmail's deduplication that cannot be disabled. I believe gmail de-duplicates your list echo because it sees a copy in your sent folder. I wish it could be disabled :-/
If list owners wanted this to be a feature, you could configure it on a list basis, at least in mailman. However nobody does, because it's incredibly annoying :-)
Agreed. Whenever I mail a list if I have an important message I have to ask someone if the message appeared or not. I can't verify by receiving my own copy. I use mail lists every day.