'the right of regular users to mute and hide unwantes comments' should only apply on rewards-declined content. Otherwise, the rewards are coming from a shared rewards pool and the user doesn't have sole ownership over it.

Id argue that the reward pool has nothing to do with the content ownership. The reward pool does not enter into the intellectual or creative property of the content in any way.

This is a frontend issue in my mind and thus not subject to any inherent mechanic or attribute Steem has as a blockchain since the steem blockchain cannot and never will be able to deal with such specific questions of content property or human interaction.
This is the next layer where community consensus and application ownership are being discussed.
As Steemit.inc says in the post, its their call what to implement, if someone else wants to create a frontend with their own rules they can....

All that being said, i support this change.
Do i think its marginal? YES.
Do i think there are other far more important things to think about?
YES.
Do i think the Steem community is very small and the loudest members of the community fall into one extremely narrow political worldview and that it would be extremely hard to get a objective, unbiased, thought out response from them that isnt subject to the echo chamber, aggressive mentality that stems from the disdain of the mainstream social media equivalents?
Absolutely YES.

But as the question stands alone. It depends how you do it. If you do it right and watch for all the "leaks", this is a superior option to the one we have now and i support it.