[theducks]

Originally Posted by Skydog

<p class="x2DED-FIRST">&nbsp;</p>

or this:

<p class="x2TTLPG-AU"><br /></p>

Thank you for the very helpful info regarding margin-top/bottom in em (which I always use) vs. left/right in pt. I was not aware of the relationship with the zoom level.

Thank you again for your help -- it is greatly appreciated.

This is a (mostly) empty paragraph (or forced Break) that some use because:
1)They don't know how to us top/bottom margin values
2)Their device ignores margins used in #1

The problem: is these margins are indistinguishable from Scene breaks, Header spacing and a host of other uses.

IMHO trying to sledge hammer fix with Calibre is asking for a mess.
This is a case where a EPUB editor like Sigil is handy.
first)
Replace the desired cases with a new selector to distinguish these.

class="x2TTLPG-AU" -> class="scenebreak"

all you need to do in the stylesheet if no other properties need changing

.x2TTLPG-AU, scenebreak

is add a comma and the additional selector to make a group
next)
adjust the top/bottom margins for those other styles that spacing is desired

Now you should be ready to remove those other 'empty lines')