Hi 
Actually the Doc format works just fine in LibreOffice and almost all
other office suites and programs. It's only the DocX that really has
problems.
Many people don't even have any idea of what format they are using.
Windows defaults hide the file-extensions so it's difficult to find
out. Doc was around for so many years that people assume they are
still using that when they run into problems but we invariably find
that they were really on DocX and that when they do "Save As" into the
older format the problems evaporate.
From the comments it looks like there might be some problem with
trying to open some ppt (Powerpoint presentations) in some versions of
LibreOffice. I think we even had a couple of threads about that on
this mailing list. However again it's not completely certain that
they really knew what they were talking about and there is a good
chance they were really using PptX.
Any editable document is likely to appear slightly differently on each
different machine it opens on due to settings, configurations, types
of printers attached, A4 vs US Letter page sizes and so on. That is
why PDF exists as it is meant to look identical on all machines.
Sadly it's not always true now but that is the basic idea of PDF.
These slight variations are NOT really the main problem. If people
really care about the precise layout then they should really be using
a proper DTP and apparently LibreOffice (and OpenOffice) make it
really easy to move documents into LaTeX and such but people are less
likely to have heard of those and more likely to think of the
expensive alternatives (that are probably not as good) where you have
to keep buying a new program every couple of years to keep up.
However the interoperability issue is much bigger than that it's just
that people are more likely to have noticed the fairly trivial issues
so it's easier to explain it using those as examples.
Regards from
Tom 