I recently used Special:MassMessage to send a notification to 1,800+ talk pages. Rather than have the posts signed as "MediaWiki message delivery," I opted to have it signed under my own name by doing the usual [[User:Harej|Harej]]. I ended up getting two notifications about "MediaWiki message delivery" pinging me, even though they were just my own comments. But I only got two notifications, not over 1,800. Both of the notifications were from posts to Flow boards:
https://en.wikipedia.org/w/index.php?title=Topic:S9votlzzkv0yz49e&topic_showPostId=s9votmaguo7uw9jm&fromnotif=1#flow-post-s9votmaguo7uw9jm
https://en.wikipedia.org/w/index.php?title=Topic:S9vousecxfm7f5kk&topic_showPostId=s9vousj93cqgo8hg&fromnotif=1#flow-post-s9vousj93cqgo8hg
In the long term, the way MassMessage messages are attributed should be revisited, but in the meantime, it shouldn't ping me over my own message.