But you're not against hard forks, are you? In a similar thread, you claim that a few blocksize bumps might happen, even with Segregated Witness. No? Those are hard forks.
Not against hard forks that have consensus. A 75% increase threshold is contentious hard fork which I do not support at all (regardless of who wants it; if Core put such a threshold I'd be against it).
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Consensus? What does that mean? Hashpower? Non-mining nodes? Wallets? Percentage of BTC in existence (hodlers)? What arbitrary number would you like, if 75% is too low?