Here some news, there a blog post. During these days, Microsoft is publishing on different places on the web, and not only for you, it is impossible to follow all . Therefore I do not know, where I have read the message, but it is more interesting, what we may read here.
Upcoming changes to SharePoint and OneDrive for Business APIs to support # and % in file names
Our old Groove Client has more Limits on characters and the Next Generation Sync Client (NGSC) only have trouble with # and %. That’s the last two characters.
It is important, that the Client will support these, but on the server side Microsoft programmers have to implement another functionality in SharePoint Online and for the Rest of the world have to implement changes in the API.
So in the near future we and all our Users will see less error messages like the message above. There is no time frame, but I have seen the first quarter 2017, and I think, it will come in the second quarter 2017.
Link
Roadmap Office 365 OneDrive for Business filename support improvements
Hans Brender's Blog 
On an Ignite OneDrive roadmap slide it said these two forbidden characters will be removed in 2017Q2. On the same slide (same timeline): the max path length will be removed. The text is rather cryptic, It is not clear if and what the new max length will be. It would be very cool if this is true.
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