aakk9999 - 8:26 pm on Jun 27, 2013 (gmt 0)
It may depend on:
- what kind of blog is. Some blogs are about the subjects where people would naturally want to add link to show an example of something etc.
- whether the external links in comments are nofollow.
- how well your blog is moderated
If your comments links are nofollow, you may decide to allow visitors to drop links, but I would still moderate as having links to spammy site is not a good user experience.
If you moderate your blog comments, you check the links very regularly and remove the ones that go to spammy sites, you may decide to leave the option of having links in comments and then weed out links to spammy sites.
If you do not moderate your comments, the easiest is to not allow links in comments, but as a minimum the links should be nofollow.