Even though according to
RTWIKI-15 the request of "Do not autosave unless there have been actual changes to the text." was implemented, it doesn't seem to be generally truth. The page is still saved when "Autosave" is checked at every specified interval, even though user makes no changes to the page:
Note that it doesn't seem to matter whether WYSIWYG or plain text ("Wiki") editor is used. I suppose the "Autosave" function shouldn't depend on the type of editor by-design anyway...