As Dave_L said, in Threads there are 2 email fields when a user edits their profile.

"Administrative purposes" is only seen by Admins and used by the system to mail lost passwords etc....

"Displayed on Posts" is actually the email that's displayed in thir profile that regular users can see.

Users can renter the "email displayed on posts" in their profile.

So anyone who wants to display it, can do so simply by adding the email address into their profile. If they don't want to display it, they simply don't fill it in.
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Josh
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