Lol! Again, if you need to sign an office document - you're doing it wrong. That shows that you're working in an extremely undeveloped way, substituting paper with an office file and probably storing the files to some shared location just like they did in filing cabinets of old. Any developed organizations should have a proper app to do the job instead.The Open Office XML is an open and free to use standard for anyone, that's not the problem these days. You still have to implement features in software. As I've mentioned before, LibreOffice is totally unaware of ink in Office documents. But the data for the ink is clearly available in the XML, LibreOffice simply doesn't do anything with it, it has nothing to do with proprietary files and formats.
And you might say "So what, nobody uses ink." Until somebody does. Capturing signatures digitally isn't uncommon these days. There have been a number of occasions that I've received a Word document over the years that needed to be signed and I just signed it on my tablet and emailed it back. Had they been using LibreWrite, the time wasted on dealing with something just this simple would pay for Office for the month easily.
I also can't find any reason why I would need some customers 'ink' signature on a file as I handle the data inside the file. I simply have no use for such a thing. The only part of the whole project when you even need office files is the definition stage before a proper integration is built that takes care of data synchronization.