If I mute a category, it (appropriately) hides it from the Categories list. I like this behavior (as do my users) because it lets users opt-out of uninteresting discussions.
However, muting subcategories does not behave the same way.
Here, I have sysadmins and devs muted because I am neither, and all that jargon is alien to me.
Subcategories should behave the same way as categories do; disappear from the categories page when muted.
With a lot of users like ours, with very intense but varied interests, they have expressed a lot of desire to hide categories they aren’t interested in to make navigating the Categories page easier and less cluttered.
I also support the expected behavior of muting/watching a category muting/watching its subcategories unless specifically unmuted. See here and here.