All fixes are nothing but temporary.
Auot-ruler, spell check etc. Nothing works on a permanent basis.
I have the disappearing cursor on 90% of the documents I work on. I can make it go away on purpose just by hitting Ctrl+S (saving the document). If I don't save the cursor stays visible. But only a foll would not save often when working with Ms Word...
The only temporary/easy fix I found is the following:
You can bring back the cursor by changing focus to another Word window, then back to the original file: bam, the cursor is there again.
Microsoft people should be ashamed that this issue has been there for so many years. They even claimed it was fixed with the 14.4 update, which, as noted already in this forum, is not true. I have the latest updates 14,6 and the cursor still disappears regularly.
This issue has gone worse with Yosemite, and even more frequent since I upgraded to Capitan, so I surmise that Apple is not helping either... Actually with Mountain Lion it was only half as bad.