Thank you for your help!
First, I tried your suggestion to change the preferences to OSX importer but it did not keep the italics on the import.
Then I opened the RTF I had exported from Jer's in LibreOffice (I don't have MSWord), added a small amount of text, Saved-As RTF, and when I imported that RTF to Storyist, the italics were there--yay!
Unfortunately, the chapters were not there. I realized the Storyist import dialogue box was different:
When I import the RTF I exported from Jer's, step one of three in the Storyist Import Assistant window is "Apply Styles by Matching Text", and the resultant import is divided into chapters using the word "Chapter", but no italics are imported.
When I import the RTF I saved from LibreWriter, step 1 of three is: "Replace Styles", and despite selecting Chapter from the different choices the resultant import is not divided into chapters--except in Normal, where every sentence becomes a chapter.
I assume this is a styles issue and I could go through and change each Chapter title to a heading style manually, but this is a 230K word book with 64 chapters and I was hoping I wouldn't have to do that.
Attached are the small, test RTFs I exported from Jer's Novel Writer and modified in LIbreWriter.
italics test.rtfitalics test 2.rtfitalics test 3.rtf