Just tried a word file, as far as I can tell there is no support for track changes. There is simple comment support and that is it.
Edit: I did some testing on a file within my Dropbox and can confirm that track changes isn't supported. A document created on a computer and saved with track changes turned on will be fully editible in Hancom Word and any changes made from within Hancom are not flagged by Hancom as edits. This means that if you edit a file within Hancom with the anticipation of seeing those edits on a computer as flagged changes they will not be, instead it will appear as though the content that is visible is completely original. What's worse, any edits that others may have made to files that were clearly marked in MS Word on a computer will not be visible as edits from within Hancom. Suffice it to say, working with documents collaboratively could prove to be difficult since changes made by users of Hancom on the tablet side AND users of Word on the PC side will not be able to determine what edits were made by others within the documents.
If im right this would mean that saving separate copies of files and using a computer to run compare versions would be the only way to verify changes that were made to documents in hancom word on the tablet. Either that or being diligent with adding comments in hancom using the comment feature each time you make a change.
That said, I still find hancom word the best I've seen on android for handling documents. My business files open up looking as they do on my workstation and much of the editing features that I need are there for me. I'm not one to want to do production type work on a tablet so if I have a document I need to edit while I'm on the go and my edits are going to be extensive I'll probably weigh heavily whether or not I'll reach for my laptop or wait to get back to the office.
If you're still making your purchase decision and this is a key issue you may want to consider a surface pro. At least with that you're assured a full version of office.
@encelle111: I'd like to thank you for asking this question. I'm not sure how long it would have taken me to realize that track changes are completely invisible in Hancom. I suspect it would have been sooner than the realization that any edits that I did do to email attached office files would be invisible to the people that I sent them back to. At least now I know not to expect people to see my edits and that if it is important that they do I need to format in such a way as to let them know (either by adding a comment or by changing font colors or highlighting).