That <xml> junk hitches a ride with text pasted in from Microsoft Word. The easiest way to avoid it is to paste as plaintext.

Failing that, just delete the characters on either side of the junk-chunk and retype them.

You can also (if you dare) switch to HTML edit mode and delete it the old-fashioned way... if you don't mind being terrified by just how much crap that sneaks in with each paste.

By the time you read this, though, I'll have already deleted the crud from your story.