I do not use any inline styling (I just map italics and bold.). Only "clean" paragraph or character styles coming from an .ott template.
I wish Word would not mess (interfere?) with any template of its own and just be happy modifying the text of the odt file it received. Maybe I ask too much...
My only reason for using Word is a special "post-OCR" macro (not coming from Microsoft) for French language. I know of no such efficient tool with LO.
But I know how to workaround these problems, using some regex.
Another "simple" problem you can check: take a standard cover image in odt. Give it a relative size (says
width 90% height 100%). Import with Word. Stay with odt. When you get back your odt and later convert to EPUB3, your image has a width of 42%. and an empty paragraph has been added just to spoil the display. Absolutely no "work" had been requested to be done on this particular image. Funny, except when you have thirty images...