So what is happening when people outpost on mastodon?
They're basically saying that there are people on this network, that they'd much prefer to be talking to *somewhere* else.
What that somewhere else is, matters. It says a great deal when people outpost to bluesky. It says they don't give a damn about independent social media for one.
And it's why a lot of people have such an emotional reaction. Even if we can't find the words as to why it's annoying.