It's entirely a matter of personal choice, VR. I prefer not to have them myself, but I have no strong objection to them. What I was objecting to, in the post to which you're probably referring, is the use of blank lines where they simply shouldn't be - eg between lines of poetry.
Note that most implementations of the MobiPocket Reader will leave a gap of about half a line between paragraphs, so adding an "explicit" blank line is not really necessary in Mobi books.
Hope you didn't read more into my post than I intended!
