To continue the theological analogy...you don't need to know anything else about DRM, other than it is EVIL incarnate...foisted upon us innocent consumer's by the Devilish publishers in an attempt to keep us manacled in bondage to a particular publisher/retailer.
Most of those word processors are/were designed to create a printed document...so it didn't matter what coding went on behind the scenes. As the electronic document age came upon us, it was very difficult to get those ponderous software developers to adjust there way of thinking. Eventually their product could "save as" a particular format (epub in this case) but it still carries all the baggage of that nasty coding that was previously hidden behind the scenes.
People are serious when they say it is sometimes easier/better to just dump your raw text into Sigil and add the basic html tags in code view.
HTML coding for an epub SHOULD be very simple...IMHO the simpler the better.
Chapter headings: <h2>Chapter One</h2>
Paragraph tags: <p>A bunch of words hopefully joined with good grammar and punctuation into a paragraph</p>
Emphasized words: <em>Italicised Words</em>
That should be about 95% of the tags you need for the HTML coding...but the other 5% are important too!
The CSS is where all the magic takes place...you can make all that basic html look beautiful (or not) just by changing the CSS file. An excellent example of this is at the
ePub Zen Garden. You can see the same basic page completely changed just by selecting different CSS styles in the top right drop-down box.
Those links I provided - the sigil video tutorial, and the HTML/CSS tutorials - are a great place to start...they will set you on the straight and narrow path - and even place your hand on the iron rod - very quickly!
Cheers!