comment author links automatically appended with rel=external nofollow

Guys,

my commenters enter their URL but when it is posted in the comment list it appears appended with %20rel=external%20nofollow/ and when clicked does not navigate to the commenters webasite.

How do I remove this text and enable the link to point to the commenters website?

I suspect this is related to an attempt to use gravatars (monsters). the gravataers showing with comments in my dashboard, which works. I can’t remember or rediscover how I turned this on.