Some but not all of the "rules" provided in various style manuals apply only to typewriter-written copy and were never intended for typeset/printed manuscript. The books all date back to an age when typewritten copy was the only format in which the written word was presented to teachers/professors and to typesetters/printers.

In addition to the various ellipsis- and dash-related issues already discussed, one very important and pervasive anomaly that often arose in the typography business ~ both when converting customers' keystrokes and also when training new employees to become typesettings ~ was the convention of double-spacing after the period at the end of a sentence. A helpful convention for manuscripts produced with monospaced characters, but completely unneccesary and inappropriate in typesetting.

Of course, nowadays most common everyday "typing" is output in a typographically sophisticated format, so none of the old "typewriter" conventions are appropriate.

Going back to the simpler issues first addressed in this thread: short paragraphs are indeed preferable to huge gray blocks of text, not only easier to read, but indeed much more likely to be read at all. And lack of capitalization (all lowercase keystroking) is moderately irritating, but not nearly so offputting and illegible as ALL CAPS ALL THE TIME.

Lowercase letters have a greater variety of shapes and can be recognized and differentiated much more easily than caps. To prove this to yourself, print out a long line or two of anything in all-lowers and also in all-caps, and then cut each line in half horziontally (i.e., so that each cut piece of paper consists of all top halves of letters, or all bottom halves.). You'll be able to read the lowercase stuff easily enough, but the half-lines of all-caps will be totally incomprehensible.