Heh, apparently I got 12 invites for private messages on Matrix a day or 2 ago. It's the same account inviting me 12 times, which was not possible to condense to a single request, for reasons.
Luckily, Matrix is blazing fast, so rejecting an invite only takes about 10 seconds. And you need to reject them individually, of course.
Then you notice that these invites aren't disappearing, even though I clicked "Reject", I got a spinner for about 10 seconds, and the screen changed to the room I was in before checking out the invite.
I want to like Matrix, but quality software is so low on their priorities that it's ridiculously hard to do so. Suggesting it to a friend is completely out of the question.