Character Viewer problem in High Sierra
The behavior of the Character Viewer used to insert Emoji's and Symbols seems to have changed in High Sierra. It no longer appears in some applications, and "Show keyboard and emoji viewers in menu bar" in Keyboard Preferences won't stay enabled--when checked, it gets unchecked when the Preference panel is closed. Character viewer also seems to pop up at odd times after closing an application as well.
In some applications, notably an online editor I use on a web page in Chrome, the Character Viewer won't come up at all (although one can cut and paste characters from another application, like TextEdit or Word).
Could I have corrupted some configuration, or has Character Viewer changed its character?
Here's an example of the oddity of the preference panel:
MacBook Pro (Retina, Mid 2012), OS X Yosemite (10.10)