I have a claim to backup. It's pretty rare, but I occasionally encounter a Word doc of some type that LibreOffice pukes on if it will open at all and sometimes flat out crashes the application. Strangely, if I use the otherwise vastly inferior (IMHO) predecessor OpenOffice, those files, so far, reliably open. So I always maintain an installed copy of OpenOffice for this rare event. I am about to install 5.1, maybe this will now be a thing of the past. It will be hard to say since it's pretty rare. I'm not bashing LibreOffice. I love LibreOffice to death. Just pointing something out.
All-in-all I think it is safe to say that word processing, mostly in the MS Office sense, is a disaster area. There is more than a couple posts above this pointing things out along the lines where someone with one version of office saves a file, and someone else one or two versions off opens it and the formatting has gone to hell despite the fact the fact the file type should be compatible between the two. I am sure most of us have been there. This is likely why PDFs are used whenever possible.
I have had the opportunity save and open files across multiple versions of LibreOffice and of different file types going back about five years. Never had a problem. This is LibreOffice to LibreOffice in the absence of MS Office.