Your understanding of soft forks is incorrect. Changes to the consensus rules implemented by soft forks are in no way optional, nor are they backwards-compatibl

Your understanding of soft forks is incorrect. Changes to the consensus rules implemented by soft forks are in no way optional, nor are they backwards-compatible [0]. Nor are soft-forking changes meaningfully more limited in scope than hard-forking changes. Soft forks, by introducing new rules referring to data unreferenced by the old rules, can be used to make almost arbitrary changes to the protocol. Bitcoin Core's planned implementation of segregated witness uses this technique, which is how it is able effectively to loosen the constraint on block sizes. The technique can be extended to implement an arbitrary increase in the blocksize as a soft fork [1], or even to change the rule that limits the final supply of bitcoin to 21 million units [2]. Name a change you want to make to the consensus rules: chances are that with enough cleverness (and a willingness to make a big enough mess) you can find a way to implement it as a soft fork. The most salient consequences of changing consensus rules by soft fork versus by hard fork, to my mind, are that (a) soft-forking changes ordinarily introduce substantial additional complexity compared to effecting the same change with a hard fork, and (b) developers can introduce changes via soft forks without having to secure the same degree of explicit consent from miners and users that hard forks require. Phenomenon (a) occurs because soft-forking changes must be implemented by roundabout mechanisms that preserve formal (but not semantic) compatibility with the old rules, whereas hard forks provide the freedom to make changes in the simplest or most technically appropriate way. Point (b) perhaps helps to explain the preference of Bitcoin Core's team for soft-forking changes: they are less constrained by the desires of users and miners under a policy of implementing changes to the consensus rules by soft fork than they would be if they were to attempt the same changes with hard forks. 0. https://medium.com/@octskyward/on-consensus-and-forks-c6a050c792e7#.kxsty3rw9 https://medium.com/@octskyward/on-consensus-and-forks-c6a050... 1. https://bitcointalk.org/index.php?topic=1296628.0 https://bitcointalk.org/index.php?topic=1296628.0 2. https://np.reddit.com/r/bitcoin_uncensored/comments/43w24e/raising_the_21_million_btc_limit_with_a_soft_fork https://np.reddit.com/r/bitcoin_uncensored/comments/43w24e/r... Edit: I encourage interested readers to verify what I have written by referring to the sources I cited or by doing their own research. Downvotes in discussions of Bitcoin here unfortunately tend to reflect the voters' loyalties in the blocksize brouhaha more than their honest assessment of whether a comment is informative and correct.