I've noticed this with extroverted NT people too. The other day someone who is obese phoned someone's mobile, and someone who is one of those extroverted loud people said to the others in the room, "if she wants to come, there will be no room for her to sit, plus she is rather large", and someone else was like "sssshhhh!! !"
I wouldn't have said something like that out loud about a person who was on the other end of a phone, but I sometimes slip out other things I shouldn't, especially at work.
See, at work there are lots of secrets people share, things that don't need to be secrets really but some people just get overparanoid and think everything must be hush-hush. So sometimes I am reluctant to open my mouth.
I never shush people, ever (probably because I don't like being sshh'd myself). So if I haven't done a task at work that I know I will get away with not doing, and I tell a trusted coworker that I didn't do it, I don't go, "I didn't do the task, sssshhh!", instead I go, "I didn't do the task, but don't say anything".
I do know that sshh has lots of hidden meanings, but that still doesn't make me feel better about it.
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Female