I am really starting to f***ing hate your WSYIWYG editor.
This bug is particularly insidious because any user editing a problematic page will start screwing it up without realizing it.

Steps to reproduce:

Create a new page

Put in this text (in Wiki markup view):

1. No formatting

   something not formatted

2. Something else not formatted

   something else not formatted

Click save.

Click edit.

In the rich text view you will see extra spaces, in the wiki view everything looks fine.

Select the rich text view then click save.

Now the web page has spaces in it. (it gets worse)

Click edit

In the rich text view you will now see even more spaces, in the wiki view you will see the spaces created last time we saved.

Select the rich text view then click save.

Now the web page has even more spaces in it.

The wiki markup is now:

1. No formatting

   something not formatted
   

    
    

2. Something else not formatted

   something else not formatted