Also, even if I don’t upgrade to v0.18, I have to live in a fediverse that have other instances that WILL, and they might pose a problem with increased spam.
A fork avoids this problem how?
I disagree, once your open source project “sprouts wings” you enter an unspoken power battle. If enough of the community disagrees with something the chance of a successful fork grows. Once a project is forked away, you no longer have any control at all.
Who's writing the code for the fork? If you see them, can you ask them to just submit the PR that the devs said they'll approve?
Right but to your other point, the admins who don't fork will send you spam.