To allow rich text formating, ckgedit may add HTML code inside the text file : when you use wikitext, the text could be less easy to read because of the additions made by ckgedit.
Just as a matter of clarification, ckgedit saves it files as ascii text files, with one exception, where it's asked to save a block of html. If you are asking someone inexperienced to use ckgedit, I would go to the configuration options and turn off font styles. Overused, or used in tables or lists, they can be problematic, unless you are experienced using them.