You won't be able to hide mounts at all until GU56 goes live. And once it does, it will be a personal setting: you won't see mounts or you will see mounts, but how folks see you will be up to their settings.
With that said, there may be a / command for that option. It's still on test, so I'm not sure yet however. You may want to log onto test and experiment by typing / strings and hitting tab to see what commands are available (ie try /hide then tab, then perhaps /mount then tab).
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