UPDATE:
Managed to replicate bug. Attempting to fix bug. See thread here for more info:
ORIGINAL POST:
It shouldn’t be thread specific. I don’t have a Mac to test on, but mute seems to be working as designed across the following setups:
Theme: Earthtones
(Working) Firefox 55 / Windows 7
(Working) Pale Moon 27 / Windows 7
(Working) Chrome Current / Windows 7
(Working) Chrome Current / Android
(Working) Firefox Focus / Android
Theme: Default Dark
(Working) Firefox 55 / Windows 7
(Working) Pale Moon 27 / Windows 7
(Working) Chrome Current / Windows 7
(Working) Chrome Current / Android
(Working) Firefox Focus / Android
I recommend closing any open Cafe tabs, opening one tab, and muting the trouble user. Alternatively, after muting somebody, reload all Cafe tabs to see it take effect.