Here a SUMMARY about the issue regarding hanja 漢字 input under macOS "Sierra"
My first take on this, on where to locate the problem of inputting hanja under macOS "Sierra" (10.12), as posted end of August on the KoreanStudies Internet Discussion List, was partially off. The issue is in fact not that Apple now dropped that functionality all together. Rather, the problem comes in because several major software companies have not updated their code yet -- and, as begun in the earlier El Capitan OS, Apple has now further changed major pieces of code in Sierra's 'kernel' (same applies to iOS 10) ... likely due to more code written by Swift (their programming language and tool).
The short version of the story is as above. In Apple's own software (e.g. their word processor "Pages") the input works fine, and even in some of Microsoft's 2016 Office programs, such as Excel, it works. Of course, for Koreanists what counts is MS Word and possibly Outlook, and there it does not work, had not been fixed under OS X El Capitan and has not been fixed for Sierra either. A workaround had been the open source application "Karabiner," a key remapping script, clearly the best of all such scripts for the Mac. Because of these code changes in the kernel, though, the present version of "Karabiner" is not anymore working. I will come to that below.
Is there a new workaround for MS Word?
Not really; presently -- mid-September 2016 -- there is not. IF using Sierra (which seems OTHERWISE more stable than OS X El Capitan) I can only suggest to use MS Word's SEARCH input field to generate hanja; that works in both, MS Word 2011 and 2016. I am referring to the search field on the top right of the document view, with the small magnifying glass:
You'd then still have to copy/paste the characters into your document's body text.
It works in that SEARCH window because that is a pre-defined element from Apple's code library, so it gets auto-created on the fly. The document body, on the other hand, is, as we would expect, Microsoft's own outdated code, and the input function is thus not working. Maybe later...
I used "F-Script" -- more particular "F-Script Anywhere" -- to look at the code element where that happens .... F-Script is an amazingly useful script for reverse engineering. The code of partially encrypted applications like MS Word can otherwise not be checked and thus not be fixed. But with F-Script (and until recently "simbl" which is now outdated), you can do that step by step, look at the various elements and Objective-C sub-routines of the Cocoa libraries, and then do some open heart surgery there and interrupt or insert a function where needed. That's lots of fun, and it can save the day. Yet, in this case, because of the kernel code changes, it is near-to-impossible to fix the issue (because MS Word still 'thinks' it works under a different OS).
We should wait for EITHER Microsoft (and others) to update their code, OR (I am more optimistic there) for Takayama Fumihiko to update his "Karabiner" script. You can easily check this from time to time at https://pqrs.org/osx/karabiner/. It seems he is also working on a new version of Karabiner, called "Karabiner-Elements" (not quite sure yet how that will be different from Karabiner itself, but it does address these kernel changes): https://github.com/tekezo/Karabiner-Elements
macOS Sierra & iOS 10 disables PPTP proxy connectivity for VPN
Since I am at it: in case you use proxy connections, e.g. to access your university library's e-resoures, or for many many other things ... be aware that macOS Sierra disables and DELETES all stored PPTP profiles during the OS upgrade. PPTP is one of several proxy protocols, and you probably do not anymore use that now if you are at a larger university or other major institution. PPTP is known to be insecure. Still, there is a whole universe of companies out there that still relies on this protocoll (it's simple to set up, that's the main reason ... and even Windows 10 still has it). I looked around, and the only application for a Mac running Sierra that allows you to still use it, with a sophisticated way around this new limitation AND being secure at the same time, is a commercial program called "Shimo" (https://www.shimovpn.com/). Works like a charm, has a very userfriendly interface, allows you to store all setup profiles, and is a wonderful tool for all sorts of connectivity tasks (offers all modern network protocolls) on the Mac.