Well what do you think that documentation is for - if not to teach. No bloody use in writing documentation for an audience that already know the product, is there? When you write documentation, you always assume that the reader knows nothing about your product! If that's true, the reader will thank you! If it's not the reader will scan the document until he finds something of interest, or leave it alone altogether.
Of course documentation is intended to provide information about the software, but a program like Geany has a wide range of users, and something that appears crystal clear to the writer may be totally opaque to a reader with different language, cultural, or background knowledge, or experience. Not to mention the delightful imprecision of the English language.
This is an open source project so why don't you put your time where your mouth is and produce improvements to the documentation instead of criticising those who use their time to provide products to share.
You could separate the documentation into reference documentation which presumes a level of expertise and does not teach and user/tutorial material for beginners which does teach.
Cheers Lex