By default blogger set only register user who can made a comment, if some readers make link in they comment, blogger automatically give them rel noffolow. I think this is fine and safe, as long as search engine not follow those links. see picture below how to set only register account can left a commnet on blog.
Login to your Dashboard > Settings > Posts and Comments , check Registered User and check Always on Comment Moderation and Click Save.
But, if those links which left by the readers bothering you, it can be hide using Jquery.
Go to Your Dashboard, Click Template > Edit HTML and Checklist Expand Widget Templates
Scrolldown below and find </head>
Right before it. paste the code below :
Save the template and try make some comment using links and see if the code work.
If you have Jquery before, delete this line :
That's it, Feel free to leave a comment