Ha! Cracked it! Well at least I know the how, if not the why.
When composing posts in blogger you can use a standard WYIWYG (what you see is what you get) text editor, or, if you know what you're doing, you can use an HTML editor.
I, and I suspect most, users use the standard text editor.
Viewing the afflicted posts in the text editor they look fine, but in the HTML editor carriage returns seem to have been inserted.
These visible CRs are not part of the formatting code, that would be the "< br / >" instruction. The spaces are chopped out where the inserted CRs appear, eg between "new" and "interface".
So a solution would be to view the post in the HTML editor and remove the CRs prior to publishing. This works but is a bit messy.
Hmmm. Just had a thought. I wonder if it's the SIZE of the window I'm pasting the Word document into.
I tend to have open windows at less than full size sIi can easily access a column of regularly used shortcut icons on the right side of my desktop. If the pane where too small to accomodate a full line of text, might it be forced into inserting those CRs?
I'll try pasting into a full width window tomorrow. At least I now know how to correct to errors if they occur.