Many people post bad comment and use abusive language this is called spamming.To over come from spam there is no gadget but you can enable captcha verification.I have seem put bad link that may go to bad sites or put bad images.you can delete comment but some blogger are very busy and can not check comment daily.I always welcome visitors to reply and i try to help.some visitor ask question or give suggestion and i love to hear their voice and try to help but i can not allow spammers.Adding verify by captcha in blog comment
Login to your Blogger blog and choose the blog
Go to settings >> posts and comments
you will see an option for word verification, just enable it
make sure it yes.Click on save settings.now on your post your visitors have to complete the word verification to publish comment.
I personally find this feature beneficial and i think every blogger should add it on their blog.