Please upgrade Mastodon. 
https://github.com/tootsuite/mastodon
I found that QOTO does not hide those statuses from muted accounts. Although I don't know if this problem is related to the software version. 
One of my following boosted a status from a user I muted. That status still appears on my QOTO timeline while I'm sure it is hidden from my timeline of another instance, where I have almost the same following list. Clients don't matter. I've tested on both web and iOS (Toot!).
@sd well i thought it works before, but after a double-check by muting a bot user that posts news on the public timeline i found it dosent work.
btw i think it has nothing to do with the masto version cuz i found an instance running the same version as this one and it works perfectly. I reckon its because of the fork of this instance.
@sd 其实还有更神奇的...就是去账号的主页里面去mute一个用户，刚mute完的时候有出现mute字样，但是退出来再进去这个mute就会消失好像你从来没有执行过这操作一样... 
@sd 那个...我刚刚尝试复现这个，然后无意中发现我这里似乎又可以mute用户了...不知道刚才发生了什么... 
@Rimekie 没错就是这样，刷新一下就知道了 ∠( ᐛ 」∠)＿