In both word (2007) and writer (3.1.0) paragraphs can opt out of line numbering at a paragraph level. On the other hand though, restarting line numbering is done at a paragraph level in writer, but at a section level in word. Which is unfortunate for an interoperability point of view.
For doc->odt conversion it’s fairly easy, just whack the restart value from the word section onto the first paragraph following that section break and all is well, though we have to be careful when munging two facts from the doc of a) paragraph opts-in/out of line numbering and b) section declares that line-numbering starts at value X, into one writer fact of “line numbering properties for a paragraph to not overwrite the other half of the fact.
On odt->doc, its not so easy. In the case where we’re re-exporting a odt which was imported from a doc then we can on export of a section have a quick peek to see if the first paragraph of that section happens to have a restart line numbering property and if so place it on the exported section. That’ll take care of doc->odt->doc round-tripping at least. where the final doc is the same as the initial doc
But for the generic odt->doc case we can’t be sure of a handy section existing right before a paragraph that uses restart line numbering so as to load the paragraph restart number onto the section. I guess we could add that circumstance to the already complicated reasons to export a section logic, its not an appealing solution, but the only one I can think of