Which browsers allow users to reveal passwords in password fields?
I already know that Windows 8, Windows 8.1, Internet Explorer 10 and Internet Explorer 11 (1). Cursory research did not reveal any other browsers with the "reveal password" feature, but do you know of any others?
Secondly I wonder Are there any UX best practices around passwords that could potentially be revealed?
My answer would be: The best practice is to not allow revealing the password in the input.
The main security risk exists for browsers that save passwords for users to use when auto-completing fields. This means a user might leave their desk and someone who knows their username could cause the password to be populated by auto-completion and then reveal the password using the browser feature.