You are so right, ClaudiusH
PerBonomi We're facing the same issue and we tested, retested as we hoped that the "Do not notify" would also kick in when moving through the API. Have a read up here if you like.
We've confirmed with Lithium that there is no way around this at the moment and in order to move a lot of our older content into a repository we must now accomplish this through launching a migration project with Lithium.
There are many ideas already around "archiving" needs and I indeed had it on my to do list to request a product enhancement for moving posts through the API. After all, it is currently our Best Alternative towards moving older topics out of the way in lack of a product functionality embedded in Lithium's software. Dear Lithium...your clients need more abilities to perform content management. Since communities have become very popular and they've been growing out of the soil as mushrooms, you must realize that many communities are mature and need to keep their community with fresh and relevant content. This is, imho, a no-brainer ;-)
Make it happen please.
I will go ahead and log an idea for this one.
Cheers
Wendy