Copy and paste from skype includes unwanted characters
As far as I know it is impossible avoid the copy of these weird characters.
But you can remove them using an editor like TextWrangler. TextWrangler has an useful menu option "Text" -> "Zap gremlins". 

This options identify and replace:


Non Ascii characters
Control characters
Null (Ascii 0) characters 


So, when I cannot avoid to copy from Skype (I suggest to use emails for important text) and I would be sure to remove all weird characters, better paste/zap/copy all the text within TextWrangler.